* subversion/mod_dav_svn/reports/replay.c

[svn.git] / subversion / libsvn_client / merge.c

/*
 * merge.c: merging
 *
 * ====================================================================
 * Copyright (c) 2000-2007 CollabNet.  All rights reserved.
 *
 * This software is licensed as described in the file COPYING, which
 * you should have received as part of this distribution.  The terms
 * are also available at http://subversion.tigris.org/license-1.html.
 * If newer versions of this license are posted there, you may use a
 * newer version instead, at your option.
 *
 * This software consists of voluntary contributions made by many
 * individuals.  For exact contribution history, see the revision
 * history and logs, available at http://subversion.tigris.org/.
 * ====================================================================
 */

/* ==================================================================== */


\f
/*** Includes ***/

#include <apr_strings.h>
#include <apr_tables.h>
#include <apr_hash.h>
#include "svn_types.h"
#include "svn_hash.h"
#include "svn_wc.h"
#include "svn_delta.h"
#include "svn_diff.h"
#include "svn_mergeinfo.h"
#include "svn_client.h"
#include "svn_string.h"
#include "svn_error.h"
#include "svn_path.h"
#include "svn_io.h"
#include "svn_utf.h"
#include "svn_pools.h"
#include "svn_config.h"
#include "svn_props.h"
#include "svn_time.h"
#include "svn_sorts.h"
#include "svn_ra.h"
#include "client.h"
#include "mergeinfo.h"
#include <assert.h>

#include "private/svn_wc_private.h"
#include "private/svn_mergeinfo_private.h"

#include "svn_private_config.h"

/*-----------------------------------------------------------------------*/
\f
/* MERGEINFO MERGE SOURCE NORMALIZATION
 *
 * Nearly any helper function herein that accepts two URL/revision
 * pairs expects one of two things to be true:
 *
 *    1.  that mergeinfo is not being recorded at all for this
 *        operation, or
 *
 *    2.  that the pairs represent two locations along a single line
 *        of version history such that there are no copies in the
 *        history of the object between the locations when treating
 *        the oldest of the two locations as non-inclusive.  In other
 *        words, if there is a copy at all between them, there is only
 *        one copy and its source was the oldest of the two locations.
 *
 * We use svn_ra_get_location_segments() to split a given range of
 * revisions across an object's history into several which obey these
 * rules.  For example, a merge between r19500 and r27567 of
 * Subversion's own /tags/1.4.5 directory gets split into sequential
 * merges of the following location pairs:
 *
 *    [/trunk:19549, /trunk:19523]
 *    (recorded in svn:mergeinfo as /trunk:19500-19523)
 *
 *    [/trunk:19523, /branches/1.4.x:25188]
 *    (recorded in svn:mergeinfo as /branches/1.4.x:19524-25188)
 *
 *    [/branches/1.4.x:25188, /tags/1.4.4@26345]
 *    (recorded in svn:mergeinfo as /tags/1.4.4:25189-26345)
 *
 *    [/tags/1.4.4@26345, /branches/1.4.5@26350]
 *    (recorded in svn:mergeinfo as /branches/1.4.5:26346-26350)
 *
 *    [/branches/1.4.5@26350, /tags/1.4.5@27567]
 *    (recorded in svn:mergeinfo as /tags/1.4.5:26351-27567)
 *
 * Our helper functions would then operate on one of these location
 * pairs at a time.
 */


/*-----------------------------------------------------------------------*/
\f
/*** Utilities ***/

/* Sanity check -- ensure that we have valid revisions to look at. */
#define ENSURE_VALID_REVISION_KINDS(rev1_kind, rev2_kind) \


/* Return SVN_ERR_UNSUPPORTED_FEATURE if URL's scheme does not
   match the scheme of the url for ADM_ACCESS's path; return
   SVN_ERR_BAD_URL if no scheme can be found for one or both urls;
   otherwise return SVN_NO_ERROR.  Use ADM_ACCESS's pool for
   temporary allocation. */
static svn_error_t *
check_scheme_match(svn_wc_adm_access_t *adm_access, const char *url)
{
  const char *path = svn_wc_adm_access_path(adm_access);
  apr_pool_t *pool = svn_wc_adm_access_pool(adm_access);
  const svn_wc_entry_t *ent;
  const char *idx1, *idx2;

  SVN_ERR(svn_wc_entry(&ent, path, adm_access, TRUE, pool));

  idx1 = strchr(url, ':');
  idx2 = strchr(ent->url, ':');

  if ((idx1 == NULL) && (idx2 == NULL))
    {
      return svn_error_createf
        (SVN_ERR_BAD_URL, NULL,
         _("URLs have no scheme ('%s' and '%s')"), url, ent->url);
    }
  else if (idx1 == NULL)
    {
      return svn_error_createf
        (SVN_ERR_BAD_URL, NULL,
         _("URL has no scheme: '%s'"), url);
    }
  else if (idx2 == NULL)
    {
      return svn_error_createf
        (SVN_ERR_BAD_URL, NULL,
         _("URL has no scheme: '%s'"), ent->url);
    }
  else if (((idx1 - url) != (idx2 - ent->url))
           || (strncmp(url, ent->url, idx1 - url) != 0))
    {
      return svn_error_createf
        (SVN_ERR_UNSUPPORTED_FEATURE, NULL,
         _("Access scheme mixtures not yet supported ('%s' and '%s')"),
         url, ent->url);
    }

  /* else */

  return SVN_NO_ERROR;
}


/*-----------------------------------------------------------------------*/
\f
/*** Repos-Diff Editor Callbacks ***/


typedef struct merge_cmd_baton_t {
  svn_boolean_t force;
  svn_boolean_t dry_run;
  svn_boolean_t record_only;          /* Whether to only record mergeinfo. */
  svn_boolean_t sources_ancestral;    /* Whether the left-side merge source is
                                         an ancestor of the right-side, or
                                         vice-versa (history-wise). */
  svn_boolean_t same_repos;           /* Whether the merge source repository
                                         is the same repository as the
                                         target.  Defaults to FALSE if DRY_RUN
                                         is TRUE.*/
  svn_boolean_t mergeinfo_capable;    /* Whether the merge source server
                                         is capable of Merge Tracking. */
  svn_boolean_t ignore_ancestry;      /* Are we ignoring ancestry (and by
                                         extension, mergeinfo)?  FALSE if
                                         SOURCES_ANCESTRAL is FALSE. */
  svn_boolean_t target_missing_child; /* Whether working copy target of the
                                         merge is missing any immediate
                                         children. */
  svn_boolean_t operative_merge;      /* Whether any changes were actually
                                         made as a result of this merge. */
  svn_boolean_t override_set;         /* get_mergeinfo_paths set some override
                                         mergeginfo - see criteria 3) in
                                         get_mergeinfo_paths' comments. */
  const char *added_path;             /* Set to the dir path whenever the
                                         dir is added as a child of a
                                         versioned dir (dry-run only) */
  const char *target;                 /* Working copy target of merge */
  const char *url;                    /* The second URL in the merge */
  svn_client_ctx_t *ctx;              /* Client context for callbacks, etc. */

  /* Whether invocation of the merge_file_added() callback required
     delegation to the merge_file_changed() function for the file
     currently being merged.  This info is used to detect whether a
     file on the left side of a 3-way merge actually exists (important
     because it's created as an empty temp file on disk regardless).*/
  svn_boolean_t add_necessitated_merge;

  /* The list of paths for entries we've deleted, used only when in
     dry_run mode. */
  apr_hash_t *dry_run_deletions;

  /* The list of any paths which remained in conflict after a
     resolution attempt was made.  We track this in-memory, rather
     than just using WC entry state, since the latter doesn't help us
     when in dry_run mode. */
  apr_hash_t *conflicted_paths;

  /* The diff3_cmd in ctx->config, if any, else null.  We could just
     extract this as needed, but since more than one caller uses it,
     we just set it up when this baton is created. */
  const char *diff3_cmd;
  const apr_array_header_t *merge_options;

  /* RA sessions used throughout a merge operation.  Opened/re-parented
     as needed. */
  svn_ra_session_t *ra_session1;
  svn_ra_session_t *ra_session2;

  /* Flag indicating the fact target has everything merged already,
     for the sake of children's merge to work it sets itself a dummy
     merge range of requested_end_rev:requested_end_rev. */
  svn_boolean_t target_has_dummy_merge_range;

  apr_pool_t *pool;
} merge_cmd_baton_t;

apr_hash_t *
svn_client__dry_run_deletions(void *merge_cmd_baton)
{
  merge_cmd_baton_t *merge_b = merge_cmd_baton;
  return merge_b->dry_run_deletions;
}

/* Used to avoid spurious notifications (e.g. conflicts) from a merge
   attempt into an existing target which would have been deleted if we
   weren't in dry_run mode (issue #2584).  Assumes that WCPATH is
   still versioned (e.g. has an associated entry). */
static APR_INLINE svn_boolean_t
dry_run_deleted_p(merge_cmd_baton_t *merge_b, const char *wcpath)
{
  return (merge_b->dry_run &&
          apr_hash_get(merge_b->dry_run_deletions, wcpath,
                       APR_HASH_KEY_STRING) != NULL);
}

/* Return whether any WC path was put in conflict by the merge
   operation corresponding to MERGE_B. */
static APR_INLINE svn_boolean_t
is_path_conflicted_by_merge(merge_cmd_baton_t *merge_b)
{
  return (merge_b->conflicted_paths &&
          apr_hash_count(merge_b->conflicted_paths) > 0);
}

/* A svn_wc_diff_callbacks2_t function.  Used for both file and directory
   property merges. */
static svn_error_t *
merge_props_changed(svn_wc_adm_access_t *adm_access,
                    svn_wc_notify_state_t *state,
                    const char *path,
                    const apr_array_header_t *propchanges,
                    apr_hash_t *original_props,
                    void *baton)
{
  apr_array_header_t *props;
  merge_cmd_baton_t *merge_b = baton;
  svn_client_ctx_t *ctx = merge_b->ctx;
  apr_pool_t *subpool = svn_pool_create(merge_b->pool);
  svn_error_t *err;

  SVN_ERR(svn_categorize_props(propchanges, NULL, NULL, &props, subpool));

  /* We only want to merge "regular" version properties:  by
     definition, 'svn merge' shouldn't touch any data within .svn/  */
  if (props->nelts)
    {
      /* svn_wc_merge_props() requires ADM_ACCESS to be the access for
         the parent of PATH. Since the advent of merge tracking,
         do_directory_merge() may call this (indirectly) with
         the access for the merge_b->target instead (issue #2781).
         So, if we have the wrong access, get the right one. */
      if (svn_path_compare_paths(svn_wc_adm_access_path(adm_access),
                                 path) != 0)
        SVN_ERR(svn_wc_adm_probe_try3(&adm_access, adm_access, path,
                                      TRUE, -1, ctx->cancel_func,
                                      ctx->cancel_baton, subpool));

      err = svn_wc_merge_props2(state, path, adm_access, original_props, props,
                                FALSE, merge_b->dry_run, ctx->conflict_func,
                                ctx->conflict_baton, subpool);
      if (err && (err->apr_err == SVN_ERR_ENTRY_NOT_FOUND
                  || err->apr_err == SVN_ERR_UNVERSIONED_RESOURCE))
        {
          /* if the entry doesn't exist in the wc, just 'skip' over
             this part of the tree-delta. */
          if (state)
            *state = svn_wc_notify_state_missing;
          svn_error_clear(err);
          svn_pool_destroy(subpool);
          return SVN_NO_ERROR;
        }
      else if (err)
        return err;
    }

  svn_pool_destroy(subpool);
  return SVN_NO_ERROR;
}

/* Contains any state collected while resolving conflicts. */
typedef struct
{
  /* The wrapped callback and baton. */
  svn_wc_conflict_resolver_func_t wrapped_func;
  void *wrapped_baton;

  /* The list of any paths which remained in conflict after a
     resolution attempt was made. */
  apr_hash_t **conflicted_paths;

  /* Pool used in notification_receiver() to avoid the iteration
     sub-pool which is passed in, then subsequently destroyed. */
  apr_pool_t *pool;
} conflict_resolver_baton_t;

/* An implementation of the svn_wc_conflict_resolver_func_t interface.
   We keep a record of paths which remain in conflict after any
   resolution attempt from BATON->wrapped_func. */
static svn_error_t *
conflict_resolver(svn_wc_conflict_result_t **result,
                  const svn_wc_conflict_description_t *description,
                  void *baton, apr_pool_t *pool)
{
  svn_error_t *err;
  conflict_resolver_baton_t *conflict_b = baton;

  if (conflict_b->wrapped_func)
    err = (*conflict_b->wrapped_func)(result, description,
                                      conflict_b->wrapped_baton, pool);
  else
    {
      /* If we have no wrapped callback to invoke, then we still need
         to behave like a proper conflict-callback ourselves.  */
      *result = svn_wc_create_conflict_result(svn_wc_conflict_choose_postpone,
                                              NULL, pool);
      err = SVN_NO_ERROR;
    }

  /* Keep a record of paths still in conflict after the resolution attempt. */
  if ((! conflict_b->wrapped_func)
      || (*result && ((*result)->choice == svn_wc_conflict_choose_postpone)))
    {
      const char *conflicted_path = apr_pstrdup(conflict_b->pool,
                                                description->path);

      if (*conflict_b->conflicted_paths == NULL)
        *conflict_b->conflicted_paths = apr_hash_make(conflict_b->pool);

      apr_hash_set(*conflict_b->conflicted_paths, conflicted_path,
                   APR_HASH_KEY_STRING, conflicted_path);
    }

  return err;
}

/* A svn_wc_diff_callbacks2_t function. */
static svn_error_t *
merge_file_changed(svn_wc_adm_access_t *adm_access,
                   svn_wc_notify_state_t *content_state,
                   svn_wc_notify_state_t *prop_state,
                   const char *mine,
                   const char *older,
                   const char *yours,
                   svn_revnum_t older_rev,
                   svn_revnum_t yours_rev,
                   const char *mimetype1,
                   const char *mimetype2,
                   const apr_array_header_t *prop_changes,
                   apr_hash_t *original_props,
                   void *baton)
{
  merge_cmd_baton_t *merge_b = baton;
  apr_pool_t *subpool = svn_pool_create(merge_b->pool);
  svn_boolean_t merge_required = TRUE;
  enum svn_wc_merge_outcome_t merge_outcome;

  /* Easy out:  no access baton means there ain't no merge target */
  if (adm_access == NULL)
    {
      if (content_state)
        *content_state = svn_wc_notify_state_missing;
      if (prop_state)
        *prop_state = svn_wc_notify_state_missing;
      svn_pool_destroy(subpool);
      return SVN_NO_ERROR;
    }

  /* Other easy outs:  if the merge target isn't under version
     control, or is just missing from disk, fogettaboutit.  There's no
     way svn_wc_merge3() can do the merge. */
  {
    const svn_wc_entry_t *entry;
    svn_node_kind_t kind;

    SVN_ERR(svn_wc_entry(&entry, mine, adm_access, FALSE, subpool));
    SVN_ERR(svn_io_check_path(mine, &kind, subpool));

    /* ### a future thought:  if the file is under version control,
       but the working file is missing, maybe we can 'restore' the
       working file from the text-base, and then allow the merge to run?  */

    if ((! entry) || (kind != svn_node_file))
      {
        if (content_state)
          *content_state = svn_wc_notify_state_missing;
        if (prop_state)
          *prop_state = svn_wc_notify_state_missing;
        svn_pool_destroy(subpool);
        return SVN_NO_ERROR;
      }
  }

  /* ### TODO: Thwart attempts to merge into a path that has
     ### unresolved conflicts.  This needs to be smart enough to deal
     ### with tree conflicts!
  if (is_path_conflicted_by_merge(merge_b, mine))
    {
      *content_state = svn_wc_notify_state_conflicted;
      return svn_error_createf(SVN_ERR_WC_FOUND_CONFLICT, NULL,
                               _("Path '%s' is in conflict, and must be "
                                 "resolved before the remainder of the "
                                 "requested merge can be applied"), mine);
    }
  */

  /* This callback is essentially no more than a wrapper around
     svn_wc_merge3().  Thank goodness that all the
     diff-editor-mechanisms are doing the hard work of getting the
     fulltexts! */

  /* Do property merge before text merge so that keyword expansion takes
     into account the new property values. */
  if (prop_changes->nelts > 0)
    SVN_ERR(merge_props_changed(adm_access, prop_state, mine, prop_changes,
                                original_props, baton));
  else
    if (prop_state)
      *prop_state = svn_wc_notify_state_unchanged;

  if (older)
    {
      svn_boolean_t has_local_mods;
      SVN_ERR(svn_wc_text_modified_p(&has_local_mods, mine, FALSE,
                                     adm_access, subpool));

      /* Special case:  if a binary file's working file is
         exactly identical to the 'left' side of the merge, then don't
         allow svn_wc_merge to produce a conflict.  Instead, just
         overwrite the working file with the 'right' side of the
         merge.  Why'd we check for local mods above?  Because we want
         to do a different notification depending on whether or not
         the file was locally modified.

         Alternately, if the 'left' side of the merge doesn't exist in
         the repository, and the 'right' side of the merge is
         identical to the WC, pretend we did the merge (a no-op). */
      if ((mimetype1 && svn_mime_type_is_binary(mimetype1))
          || (mimetype2 && svn_mime_type_is_binary(mimetype2)))
        {
          /* For adds, the 'left' side of the merge doesn't exist. */
          svn_boolean_t older_revision_exists =
              !merge_b->add_necessitated_merge;
          svn_boolean_t same_contents;
          SVN_ERR(svn_io_files_contents_same_p(&same_contents,
                                               (older_revision_exists ?
                                                older : yours),
                                               mine, subpool));
          if (same_contents)
            {
              if (older_revision_exists && !merge_b->dry_run)
                SVN_ERR(svn_io_file_rename(yours, mine, subpool));
              merge_outcome = svn_wc_merge_merged;
              merge_required = FALSE;
            }
        }

      if (merge_required)
        {
          /* xgettext: the '.working', '.merge-left.r%ld' and
             '.merge-right.r%ld' strings are used to tag onto a file
             name in case of a merge conflict */
          const char *target_label = _(".working");
          const char *left_label = apr_psprintf(subpool,
                                                _(".merge-left.r%ld"),
                                                older_rev);
          const char *right_label = apr_psprintf(subpool,
                                                 _(".merge-right.r%ld"),
                                                 yours_rev);
          conflict_resolver_baton_t conflict_baton =
            { merge_b->ctx->conflict_func, merge_b->ctx->conflict_baton,
              &merge_b->conflicted_paths, merge_b->pool };
          SVN_ERR(svn_wc_merge3(&merge_outcome,
                                older, yours, mine, adm_access,
                                left_label, right_label, target_label,
                                merge_b->dry_run, merge_b->diff3_cmd,
                                merge_b->merge_options, prop_changes,
                                conflict_resolver, &conflict_baton,
                                subpool));
        }

      if (content_state)
        {
          if (merge_outcome == svn_wc_merge_conflict)
            *content_state = svn_wc_notify_state_conflicted;
          else if (has_local_mods
                   && merge_outcome != svn_wc_merge_unchanged)
            *content_state = svn_wc_notify_state_merged;
          else if (merge_outcome == svn_wc_merge_merged)
            *content_state = svn_wc_notify_state_changed;
          else if (merge_outcome == svn_wc_merge_no_merge)
            *content_state = svn_wc_notify_state_missing;
          else /* merge_outcome == svn_wc_merge_unchanged */
            *content_state = svn_wc_notify_state_unchanged;
        }
    }

  svn_pool_destroy(subpool);
  return SVN_NO_ERROR;
}

/* A svn_wc_diff_callbacks2_t function. */
static svn_error_t *
merge_file_added(svn_wc_adm_access_t *adm_access,
                 svn_wc_notify_state_t *content_state,
                 svn_wc_notify_state_t *prop_state,
                 const char *mine,
                 const char *older,
                 const char *yours,
                 svn_revnum_t rev1,
                 svn_revnum_t rev2,
                 const char *mimetype1,
                 const char *mimetype2,
                 const apr_array_header_t *prop_changes,
                 apr_hash_t *original_props,
                 void *baton)
{
  merge_cmd_baton_t *merge_b = baton;
  apr_pool_t *subpool = svn_pool_create(merge_b->pool);
  svn_node_kind_t kind;
  const char *copyfrom_url;
  const char *child;
  int i;
  apr_hash_t *new_props;

  /* In most cases, we just leave prop_state as unknown, and let the
     content_state what happened, so we set prop_state here to avoid that
     below. */
  if (prop_state)
    *prop_state = svn_wc_notify_state_unknown;

  /* Apply the prop changes to a new hash table. */
  new_props = apr_hash_copy(subpool, original_props);
  for (i = 0; i < prop_changes->nelts; ++i)
    {
      const svn_prop_t *prop = &APR_ARRAY_IDX(prop_changes, i, svn_prop_t);
      apr_hash_set(new_props, prop->name, APR_HASH_KEY_STRING, prop->value);
    }

  /* Easy out:  if we have no adm_access for the parent directory,
     then this portion of the tree-delta "patch" must be inapplicable.
     Send a 'missing' state back;  the repos-diff editor should then
     send a 'skip' notification. */
  if (! adm_access)
    {
      if (merge_b->dry_run && merge_b->added_path
          && svn_path_is_child(merge_b->added_path, mine, subpool))
        {
          if (content_state)
            *content_state = svn_wc_notify_state_changed;
          if (prop_state && apr_hash_count(new_props))
            *prop_state = svn_wc_notify_state_changed;
        }
      else
        *content_state = svn_wc_notify_state_missing;
      svn_pool_destroy(subpool);
      return SVN_NO_ERROR;
    }

  SVN_ERR(svn_io_check_path(mine, &kind, subpool));
  switch (kind)
    {
    case svn_node_none:
      {
        const svn_wc_entry_t *entry;
        SVN_ERR(svn_wc_entry(&entry, mine, adm_access, FALSE, subpool));
        if (entry && entry->schedule != svn_wc_schedule_delete)
          {
            /* It's versioned but missing. */
            if (content_state)
              *content_state = svn_wc_notify_state_obstructed;
            svn_pool_destroy(subpool);
            return SVN_NO_ERROR;
          }
        if (! merge_b->dry_run)
          {
            child = svn_path_is_child(merge_b->target, mine, subpool);
            if (child != NULL)
              copyfrom_url = svn_path_url_add_component(merge_b->url, child,
                                                        subpool);
            else
              copyfrom_url = merge_b->url;
            SVN_ERR(check_scheme_match(adm_access, copyfrom_url));

            /* Since 'mine' doesn't exist, and this is
               'merge_file_added', I hope it's safe to assume that
               'older' is empty, and 'yours' is the full file.  Merely
               copying 'yours' to 'mine', isn't enough; we need to get
               the whole text-base and props installed too, just as if
               we had called 'svn cp wc wc'. */
            SVN_ERR(svn_wc_add_repos_file2(mine, adm_access, yours, NULL,
                                           new_props, NULL, copyfrom_url,
                                           rev2, subpool));
          }
        if (content_state)
          *content_state = svn_wc_notify_state_changed;
        if (prop_state && apr_hash_count(new_props))
          *prop_state = svn_wc_notify_state_changed;
      }
      break;
    case svn_node_dir:
      if (content_state)
        {
          /* directory already exists, is it under version control? */
          const svn_wc_entry_t *entry;
          SVN_ERR(svn_wc_entry(&entry, mine, adm_access, FALSE, subpool));

          if (entry && dry_run_deleted_p(merge_b, mine))
            *content_state = svn_wc_notify_state_changed;
          else
            /* this will make the repos_editor send a 'skipped' message */
            *content_state = svn_wc_notify_state_obstructed;
        }
      break;
    case svn_node_file:
      {
        /* file already exists, is it under version control? */
        const svn_wc_entry_t *entry;
        SVN_ERR(svn_wc_entry(&entry, mine, adm_access, FALSE, subpool));

        /* If it's an unversioned file, don't touch it.  If it's scheduled
           for deletion, then rm removed it from the working copy and the
           user must have recreated it, don't touch it */
        if (!entry || entry->schedule == svn_wc_schedule_delete)
          {
            /* this will make the repos_editor send a 'skipped' message */
            if (content_state)
              *content_state = svn_wc_notify_state_obstructed;
          }
        else
          {
            if (dry_run_deleted_p(merge_b, mine))
              {
                if (content_state)
                  *content_state = svn_wc_notify_state_changed;
              }
            else
              {
                /* Indicate that we merge because of an add to handle a
                   special case for binary files with no local mods. */
                  merge_b->add_necessitated_merge = TRUE;

                  SVN_ERR(merge_file_changed(adm_access, content_state,
                                             prop_state, mine, older, yours,
                                             rev1, rev2,
                                             mimetype1, mimetype2,
                                             prop_changes, original_props,
                                             baton));

                /* Reset the state so that the baton can safely be reused
                   in subsequent ops occurring during this merge. */
                  merge_b->add_necessitated_merge = FALSE;
              }
          }
        break;
      }
    default:
      if (content_state)
        *content_state = svn_wc_notify_state_unknown;
      break;
    }

  svn_pool_destroy(subpool);
  return SVN_NO_ERROR;
}

/* A svn_wc_diff_callbacks2_t function. */
static svn_error_t *
merge_file_deleted(svn_wc_adm_access_t *adm_access,
                   svn_wc_notify_state_t *state,
                   const char *mine,
                   const char *older,
                   const char *yours,
                   const char *mimetype1,
                   const char *mimetype2,
                   apr_hash_t *original_props,
                   void *baton)
{
  merge_cmd_baton_t *merge_b = baton;
  apr_pool_t *subpool = svn_pool_create(merge_b->pool);
  svn_node_kind_t kind;
  svn_wc_adm_access_t *parent_access;
  const char *parent_path;
  svn_error_t *err;

  /* Easy out:  if we have no adm_access for the parent directory,
     then this portion of the tree-delta "patch" must be inapplicable.
     Send a 'missing' state back;  the repos-diff editor should then
     send a 'skip' notification. */
  if (! adm_access)
    {
      if (state)
        *state = svn_wc_notify_state_missing;
      svn_pool_destroy(subpool);
      return SVN_NO_ERROR;
    }

  SVN_ERR(svn_io_check_path(mine, &kind, subpool));
  switch (kind)
    {
    case svn_node_file:
      svn_path_split(mine, &parent_path, NULL, subpool);
      SVN_ERR(svn_wc_adm_retrieve(&parent_access, adm_access, parent_path,
                                  subpool));
      /* Passing NULL for the notify_func and notify_baton because
         repos_diff.c:delete_entry() will do it for us. */
      err = svn_client__wc_delete(mine, parent_access, merge_b->force,
                                  merge_b->dry_run, FALSE, NULL, NULL,
                                  merge_b->ctx, subpool);
      if (err && state)
        {
          *state = svn_wc_notify_state_obstructed;
          svn_error_clear(err);
        }
      else if (state)
        {
          *state = svn_wc_notify_state_changed;
        }
      break;
    case svn_node_dir:
      if (state)
        *state = svn_wc_notify_state_obstructed;
      break;
    case svn_node_none:
      /* file is already non-existent, this is a no-op. */
      if (state)
        *state = svn_wc_notify_state_missing;
      break;
    default:
      if (state)
        *state = svn_wc_notify_state_unknown;
      break;
    }

  svn_pool_destroy(subpool);
  return SVN_NO_ERROR;
}

/* A svn_wc_diff_callbacks2_t function. */
static svn_error_t *
merge_dir_added(svn_wc_adm_access_t *adm_access,
                svn_wc_notify_state_t *state,
                const char *path,
                svn_revnum_t rev,
                void *baton)
{
  merge_cmd_baton_t *merge_b = baton;
  apr_pool_t *subpool = svn_pool_create(merge_b->pool);
  svn_node_kind_t kind;
  const svn_wc_entry_t *entry;
  const char *copyfrom_url, *child;

  /* Easy out:  if we have no adm_access for the parent directory,
     then this portion of the tree-delta "patch" must be inapplicable.
     Send a 'missing' state back;  the repos-diff editor should then
     send a 'skip' notification. */
  if (! adm_access)
    {
      if (state)
        {
          if (merge_b->dry_run && merge_b->added_path
              && svn_path_is_child(merge_b->added_path, path, subpool))
            *state = svn_wc_notify_state_changed;
          else
            *state = svn_wc_notify_state_missing;
        }
      svn_pool_destroy(subpool);
      return SVN_NO_ERROR;
    }

  child = svn_path_is_child(merge_b->target, path, subpool);
  assert(child != NULL);
  copyfrom_url = svn_path_url_add_component(merge_b->url, child, subpool);
  SVN_ERR(check_scheme_match(adm_access, copyfrom_url));

  SVN_ERR(svn_io_check_path(path, &kind, subpool));
  switch (kind)
    {
    case svn_node_none:
      SVN_ERR(svn_wc_entry(&entry, path, adm_access, FALSE, subpool));
      if (entry && entry->schedule != svn_wc_schedule_delete)
        {
          /* Versioned but missing */
          if (state)
            *state = svn_wc_notify_state_obstructed;
          svn_pool_destroy(subpool);
          return SVN_NO_ERROR;
        }
      if (merge_b->dry_run)
        merge_b->added_path = apr_pstrdup(merge_b->pool, path);
      else
        {
          SVN_ERR(svn_io_make_dir_recursively(path, subpool));
          SVN_ERR(svn_wc_add2(path, adm_access,
                              copyfrom_url, rev,
                              merge_b->ctx->cancel_func,
                              merge_b->ctx->cancel_baton,
                              NULL, NULL, /* don't pass notification func! */
                              subpool));

        }
      if (state)
        *state = svn_wc_notify_state_changed;
      break;
    case svn_node_dir:
      /* Adding an unversioned directory doesn't destroy data */
      SVN_ERR(svn_wc_entry(&entry, path, adm_access, TRUE, subpool));
      if (! entry || entry->schedule == svn_wc_schedule_delete)
        {
          if (!merge_b->dry_run)
            SVN_ERR(svn_wc_add2(path, adm_access,
                                copyfrom_url, rev,
                                merge_b->ctx->cancel_func,
                                merge_b->ctx->cancel_baton,
                                NULL, NULL, /* no notification func! */
                                subpool));
          else
            merge_b->added_path = apr_pstrdup(merge_b->pool, path);
          if (state)
            *state = svn_wc_notify_state_changed;
        }
      else if (state)
        {
          if (dry_run_deleted_p(merge_b, path))
            *state = svn_wc_notify_state_changed;
          else
            *state = svn_wc_notify_state_obstructed;
        }
      break;
    case svn_node_file:
      if (merge_b->dry_run)
        merge_b->added_path = NULL;

      if (state)
        {
          SVN_ERR(svn_wc_entry(&entry, path, adm_access, FALSE, subpool));

          if (entry && dry_run_deleted_p(merge_b, path))
            /* ### TODO: Retain record of this dir being added to
               ### avoid problems from subsequent edits which try to
               ### add children. */
            *state = svn_wc_notify_state_changed;
          else
            *state = svn_wc_notify_state_obstructed;
        }
      break;
    default:
      if (merge_b->dry_run)
        merge_b->added_path = NULL;
      if (state)
        *state = svn_wc_notify_state_unknown;
      break;
    }

  svn_pool_destroy(subpool);
  return SVN_NO_ERROR;
}

/* A svn_wc_diff_callbacks2_t function. */
static svn_error_t *
merge_dir_deleted(svn_wc_adm_access_t *adm_access,
                  svn_wc_notify_state_t *state,
                  const char *path,
                  void *baton)
{
  merge_cmd_baton_t *merge_b = baton;
  apr_pool_t *subpool = svn_pool_create(merge_b->pool);
  svn_node_kind_t kind;
  svn_wc_adm_access_t *parent_access;
  const char *parent_path;
  svn_error_t *err;

  /* Easy out:  if we have no adm_access for the parent directory,
     then this portion of the tree-delta "patch" must be inapplicable.
     Send a 'missing' state back;  the repos-diff editor should then
     send a 'skip' notification. */
  if (! adm_access)
    {
      if (state)
        *state = svn_wc_notify_state_missing;
      svn_pool_destroy(subpool);
      return SVN_NO_ERROR;
    }

  SVN_ERR(svn_io_check_path(path, &kind, subpool));
  switch (kind)
    {
    case svn_node_dir:
      {
        svn_path_split(path, &parent_path, NULL, subpool);
        SVN_ERR(svn_wc_adm_retrieve(&parent_access, adm_access, parent_path,
                                    subpool));
        /* Passing NULL for the notify_func and notify_baton because
           repos_diff.c:delete_entry() will do it for us. */
        err = svn_client__wc_delete(path, parent_access, merge_b->force,
                                    merge_b->dry_run, FALSE,
                                    NULL, NULL,
                                    merge_b->ctx, subpool);
        if (err && state)
          {
            *state = svn_wc_notify_state_obstructed;
            svn_error_clear(err);
          }
        else if (state)
          {
            *state = svn_wc_notify_state_changed;
          }
      }
      break;
    case svn_node_file:
      if (state)
        *state = svn_wc_notify_state_obstructed;
      break;
    case svn_node_none:
      /* dir is already non-existent, this is a no-op. */
      if (state)
        *state = svn_wc_notify_state_missing;
      break;
    default:
      if (state)
        *state = svn_wc_notify_state_unknown;
      break;
    }

  svn_pool_destroy(subpool);
  return SVN_NO_ERROR;
}

/* The main callback table for 'svn merge'.  */
static const svn_wc_diff_callbacks2_t
merge_callbacks =
  {
    merge_file_changed,
    merge_file_added,
    merge_file_deleted,
    merge_dir_added,
    merge_dir_deleted,
    merge_props_changed
  };


/*-----------------------------------------------------------------------*/
\f
/*** Merge Notification ***/


/* Contains any state collected while receiving path notifications. */
typedef struct
{
  /* The wrapped callback and baton. */
  svn_wc_notify_func2_t wrapped_func;
  void *wrapped_baton;

  /* The number of notifications received. */
  apr_uint32_t nbr_notifications;

  /* The number of operative notifications received. */
  apr_uint32_t nbr_operative_notifications;

  /* The list of merged paths. */
  apr_hash_t *merged_paths;

  /* The list of any skipped paths, which should be examined and
     cleared after each invocation of the callback. */
  apr_hash_t *skipped_paths;

  /* Flag indicating whether it is a single file merge or not. */
  svn_boolean_t is_single_file_merge;

  /* Depth first ordered list of paths that needs special care while merging.
     This defaults to NULL. For 'same_url' merge alone we set it to
     proper array. This is used by notification_receiver to put a
     merge notification begin lines. */
  apr_array_header_t *children_with_mergeinfo;

  /* The index in CHILDREN_WITH_MERGEINFO where we found the nearest ancestor
     for merged path. Default value is '-1'.*/
  int cur_ancestor_index;

  /* We use this to make a decision on merge begin line notifications. */
  merge_cmd_baton_t *merge_b;

  /* Pool used in notification_receiver() to avoid the iteration
     sub-pool which is passed in, then subsequently destroyed. */
  apr_pool_t *pool;

} notification_receiver_baton_t;


/* Finds a nearest ancestor in CHILDREN_WITH_MERGEINFO for PATH.
   CHILDREN_WITH_MERGEINFO is expected to be sorted in Depth first
   order of path. Nearest ancestor's index from
   CHILDREN_WITH_MERGEINFO is returned. */
static int
find_nearest_ancestor(apr_array_header_t *children_with_mergeinfo,
                      const char *path)
{
  int i;
  int ancestor_index = 0;

  /* This if condition is not needed as this function should be used
     from the context of same_url merge where CHILDREN_WITH_MERGEINFO
     will not be NULL and of size atleast 1. We have this if condition
     just to protect the wrong caller. */
  if (!children_with_mergeinfo)
    return 0;
  for (i = 0; i < children_with_mergeinfo->nelts; i++)
    {
      svn_client__merge_path_t *child =
        APR_ARRAY_IDX(children_with_mergeinfo, i, svn_client__merge_path_t *);
      if (svn_path_is_ancestor(child->path, path))
        ancestor_index = i;
    }
  return ancestor_index;
}


/* Our svn_wc_notify_func2_t wrapper.*/
static void
notification_receiver(void *baton, const svn_wc_notify_t *notify,
                      apr_pool_t *pool)
{
  notification_receiver_baton_t *notify_b = baton;
  svn_boolean_t is_operative_notification = FALSE;

  /* Is the notification the result of a real operative merge? */
  if (notify->content_state == svn_wc_notify_state_conflicted
      || notify->content_state == svn_wc_notify_state_merged
      || notify->content_state == svn_wc_notify_state_changed
      || notify->prop_state == svn_wc_notify_state_conflicted
      || notify->prop_state == svn_wc_notify_state_merged
      || notify->prop_state == svn_wc_notify_state_changed
      || notify->action == svn_wc_notify_update_add)
    {
      notify_b->nbr_operative_notifications++;
      is_operative_notification = TRUE;
    }

  /* If our merge sources are ancestors of one another... */
  if (notify_b->merge_b->sources_ancestral)
    {
      notify_b->nbr_notifications++;

      /* See if this is an operative directory merge. */
      if (!(notify_b->is_single_file_merge) && is_operative_notification)
        {
          int new_nearest_ancestor_index =
            find_nearest_ancestor(notify_b->children_with_mergeinfo,
                                  notify->path);
          if (new_nearest_ancestor_index != notify_b->cur_ancestor_index)
            {
              svn_client__merge_path_t *child =
                APR_ARRAY_IDX(notify_b->children_with_mergeinfo,
                              new_nearest_ancestor_index,
                              svn_client__merge_path_t *);
              notify_b->cur_ancestor_index = new_nearest_ancestor_index;
              if (!child->absent && child->remaining_ranges->nelts > 0
                  && !(new_nearest_ancestor_index == 0
                       && notify_b->merge_b->target_has_dummy_merge_range))
                {
                  svn_wc_notify_t *notify_merge_begin;
                  notify_merge_begin =
                    svn_wc_create_notify(child->path,
                                         svn_wc_notify_merge_begin, pool);
                  notify_merge_begin->merge_range =
                    APR_ARRAY_IDX(child->remaining_ranges, 0,
                                  svn_merge_range_t *);
                  if (notify_b->wrapped_func)
                    (*notify_b->wrapped_func)(notify_b->wrapped_baton,
                                              notify_merge_begin, pool);
                }
            }
        }

      if (notify->content_state == svn_wc_notify_state_merged
          || notify->content_state == svn_wc_notify_state_changed
          || notify->prop_state == svn_wc_notify_state_merged
          || notify->prop_state == svn_wc_notify_state_changed
          || notify->action == svn_wc_notify_update_add)
        {
          const char *merged_path = apr_pstrdup(notify_b->pool, notify->path);

          if (notify_b->merged_paths == NULL)
            notify_b->merged_paths = apr_hash_make(notify_b->pool);

          apr_hash_set(notify_b->merged_paths, merged_path,
                       APR_HASH_KEY_STRING, merged_path);
        }

      if (notify->action == svn_wc_notify_skip)
        {
          const char *skipped_path = apr_pstrdup(notify_b->pool, notify->path);

          if (notify_b->skipped_paths == NULL)
            notify_b->skipped_paths = apr_hash_make(notify_b->pool);

          apr_hash_set(notify_b->skipped_paths, skipped_path,
                       APR_HASH_KEY_STRING, skipped_path);
        }
    }
  /* Otherwise, our merge sources aren't ancestors of one another. */
  else if (!(notify_b->is_single_file_merge)
           && notify_b->nbr_operative_notifications == 1
           && is_operative_notification)
    {
      svn_wc_notify_t *notify_merge_begin;
      notify_merge_begin = svn_wc_create_notify(notify_b->merge_b->target,
                                                svn_wc_notify_merge_begin,
                                                pool);
      if (notify_b->wrapped_func)
        (*notify_b->wrapped_func)(notify_b->wrapped_baton, notify_merge_begin,
                                  pool);
    }

  if (notify_b->wrapped_func)
    (*notify_b->wrapped_func)(notify_b->wrapped_baton, notify, pool);
}


/*-----------------------------------------------------------------------*/
\f
/*** Determining What Remains To Be Merged ***/


/* Set *REQUESTED_RANGELIST to a list of revision ranges consisting of
   a single requested range (between URL1@REVISION1 and
   URL2@REVISION2), minus merges which originated from TARGET_URL
   which were already recorded as performed within that range.

   See `MERGEINFO MERGE SOURCE NORMALIZATION' for more requirements
   around the values of URL1, REVISION1, URL2, and REVISION2.

   Use SOURCE_ROOT_URL for all the various relative-mergeinfo-path
   calculations needed to do this work.

   RA_SESSION is an RA session whose session URL is the root URL of
   the source repository.

   NOTE: This should only be called when honoring mergeinfo.

   ### FIXME: I strongly suspect that these calculations are
   ### rename-ignorant, not accounting for the situation where the
   ### item at TARGET_URL back when merges were from it to our current
   ### merge source is not the same item at TARGET_URL now that we're
   ### trying to merge from that current merge source.  -- cmpilato
*/
static svn_error_t *
filter_reflected_revisions(apr_array_header_t **requested_rangelist,
                           const char *source_root_url,
                           const char *url1,
                           svn_revnum_t revision1,
                           const char *url2,
                           svn_revnum_t revision2,
                           svn_boolean_t inheritable,
                           const char *target_url,
                           svn_ra_session_t *ra_session,
                           svn_client_ctx_t *ctx,
                           apr_pool_t *pool)
{
  apr_array_header_t *src_rangelist_for_tgt = NULL;
  apr_hash_t *added_mergeinfo, *deleted_mergeinfo,
    *start_mergeinfo, *end_mergeinfo;
  svn_merge_range_t *range = apr_pcalloc(pool, sizeof(*range));
  svn_revnum_t min_rev = MIN(revision1, revision2);
  svn_revnum_t max_rev = MAX(revision1, revision2);
  const char *min_url = (revision1 < revision2) ? url1 : url2;
  const char *max_url = (revision1 < revision2) ? url2 : url1;
  const char *min_rel_path, *max_rel_path;

  SVN_ERR(svn_client__path_relative_to_root(&min_rel_path, min_url,
                                            source_root_url, FALSE, ra_session,
                                            NULL, pool));
  SVN_ERR(svn_client__path_relative_to_root(&max_rel_path, max_url,
                                            source_root_url, FALSE, ra_session,
                                            NULL, pool));

  /* Find any mergeinfo for TARGET_URL added to the line of history
     between URL1@REVISION1 and URL2@REVISION2. */
  SVN_ERR(svn_client__get_repos_mergeinfo(ra_session, &start_mergeinfo,
                                          min_rel_path, min_rev,
                                          svn_mergeinfo_inherited, TRUE,
                                          pool));
  SVN_ERR(svn_client__get_repos_mergeinfo(ra_session, &end_mergeinfo,
                                          max_rel_path, max_rev,
                                          svn_mergeinfo_inherited, TRUE,
                                          pool));

  SVN_ERR(svn_mergeinfo_diff(&deleted_mergeinfo, &added_mergeinfo,
                             start_mergeinfo, end_mergeinfo,
                             FALSE, pool));

  if (added_mergeinfo)
    {
      const char *mergeinfo_path;
      SVN_ERR(svn_client__path_relative_to_root(&mergeinfo_path, target_url,
                                                source_root_url, TRUE,
                                                ra_session, NULL, pool));
      src_rangelist_for_tgt = apr_hash_get(added_mergeinfo, mergeinfo_path,
                                           APR_HASH_KEY_STRING);
    }

  /* Create a single-item list of ranges with our one requested range
     in it, and then remove overlapping revision ranges from that range. */
  *requested_rangelist = apr_array_make(pool, 1, sizeof(range));
  range->start = revision1;
  range->end = revision2;
  range->inheritable = inheritable;
  APR_ARRAY_PUSH(*requested_rangelist, svn_merge_range_t *) = range;
  if (src_rangelist_for_tgt)
    SVN_ERR(svn_rangelist_remove(requested_rangelist, src_rangelist_for_tgt,
                                 *requested_rangelist,
                                 FALSE, pool));
  return SVN_NO_ERROR;
}

/* Calculate a rangelist of svn_merge_range_t *'s -- for use by
   drive_merge_report_editor()'s application of the editor to the WC
   -- by subtracting revisions which have already been merged from
   MERGEINFO_PATH into the working copy from the requested range(s)
   REQUESTED_MERGE, and storing what's left in REMAINING_RANGES.
   TARGET_MERGEINFO may be NULL.

   NOTE: This should only be called when honoring mergeinfo.  
*/
static svn_error_t *
filter_merged_revisions(apr_array_header_t **remaining_ranges,
                        const char *mergeinfo_path,
                        apr_hash_t *target_mergeinfo,
                        apr_hash_t *implicit_mergeinfo,
                        apr_array_header_t *requested_merge,
                        svn_boolean_t is_rollback,
                        const svn_wc_entry_t *entry,
                        apr_pool_t *pool)
{
  apr_array_header_t *target_rangelist = NULL;
  apr_hash_t *mergeinfo;

  if (is_rollback)
    {
      mergeinfo = svn_mergeinfo_dup(implicit_mergeinfo, pool);
      if (target_mergeinfo)
        SVN_ERR(svn_mergeinfo_merge(mergeinfo, target_mergeinfo, pool));
      target_rangelist = apr_hash_get(mergeinfo, 
                                      mergeinfo_path, APR_HASH_KEY_STRING);
      if (target_rangelist)
        {
          /* Return the intersection of the revs which are both
             already represented by the WC and are requested for
             revert.  The revert range and will need to be reversed
             for our APIs to work properly, as will the output for the
             revert to work properly. */
          requested_merge = svn_rangelist_dup(requested_merge, pool);
          SVN_ERR(svn_rangelist_reverse(requested_merge, pool));
          SVN_ERR(svn_rangelist_intersect(remaining_ranges,
                                          target_rangelist,
                                          requested_merge, pool));
          SVN_ERR(svn_rangelist_reverse(*remaining_ranges, pool));
        }
      else
        {
          *remaining_ranges = 
            apr_array_make(pool, 1, sizeof(svn_merge_range_t *));
        }
    }
  else
    {
      *remaining_ranges = requested_merge;

/* ### TODO:  Which evil shall we choose?
   ###
   ### If we allow all forward-merges not already found in recorded
   ### mergeinfo, we destroy the ability to, say, merge the whole of a
   ### branch to the trunk while automatically ignoring the revisions
   ### common to both.  That's bad.
   ###
   ### If we allow only forward-merges not found in either recorded
   ### mergeinfo or implicit mergeinfo (natural history), then the
   ### previous scenario works great, but we can't reverse-merge a
   ### previous change made to our line of history and then remake it
   ### (because the reverse-merge will leave no mergeinfo trace, and
   ### the remake-it attempt will still find the original change in
   ### natural mergeinfo.  But you know, that we happen to use 'merge'
   ### for revision undoing is somewhat unnatural anyway, so I'm
   ### finding myself having little interest in caring too much about
   ### this.  That said, if we had a way of storing reverse merge
   ### ranges, we'd be in good shape either way.
*/
#ifdef SVN_MERGE__ALLOW_ALL_FORWARD_MERGES_FROM_SELF
      if (target_mergeinfo)
        target_rangelist = apr_hash_get(target_mergeinfo, 
                                        mergeinfo_path, APR_HASH_KEY_STRING);
#else
      mergeinfo = svn_mergeinfo_dup(implicit_mergeinfo, pool);
      if (target_mergeinfo)
        SVN_ERR(svn_mergeinfo_merge(mergeinfo, target_mergeinfo, pool));
      target_rangelist = apr_hash_get(mergeinfo, 
                                      mergeinfo_path, APR_HASH_KEY_STRING);
#endif

      if (target_rangelist)
        SVN_ERR(svn_rangelist_remove(remaining_ranges, target_rangelist,
                                     requested_merge, FALSE, pool));
    }
  return SVN_NO_ERROR;
}

/* Populate *REMAINING_RANGES with a list of revision ranges
   constructed by taking after removing reflective merge
   ranges and already-merged ranges from *RANGE.  Cascade URL1,
   REVISION1, UR2, REVISION2, TARGET_MERGEINFO, IS_ROLLBACK, REL_PATH,
   RA_SESSION, ENTRY, CTX, and POOL.

   See `MERGEINFO MERGE SOURCE NORMALIZATION' for more requirements
   around the values of URL1, REVISION1, URL2, and REVISION2.

   NOTE: This should only be called when honoring mergeinfo.
*/
static svn_error_t *
calculate_remaining_ranges(apr_array_header_t **remaining_ranges,
                           const char *source_root_url,
                           const char *url1,
                           svn_revnum_t revision1,
                           const char *url2,
                           svn_revnum_t revision2,
                           svn_boolean_t inheritable,
                           apr_hash_t *target_mergeinfo,
                           apr_hash_t *implicit_mergeinfo,
                           svn_ra_session_t *ra_session,
                           const svn_wc_entry_t *entry,
                           svn_client_ctx_t *ctx,
                           apr_pool_t *pool)
{
  apr_array_header_t *requested_rangelist;
  const char *old_url;
  const char *mergeinfo_path;
  const char *primary_url = (revision1 < revision2) ? url2 : url1;

  /* Determine which of the requested ranges to consider merging... */
  SVN_ERR(svn_ra_get_session_url(ra_session, &old_url, pool));
  SVN_ERR(svn_ra_reparent(ra_session, source_root_url, pool));
  SVN_ERR(filter_reflected_revisions(&requested_rangelist, source_root_url,
                                     url1, revision1, url2, revision2,
                                     inheritable, entry->url,
                                     ra_session, ctx, pool));
  SVN_ERR(svn_ra_reparent(ra_session, old_url, pool));
  
  /* ...and of those ranges, determine which ones actually still
     need merging. */
  SVN_ERR(svn_client__path_relative_to_root(&mergeinfo_path, primary_url,
                                            source_root_url, TRUE,
                                            ra_session, NULL, pool));
  SVN_ERR(filter_merged_revisions(remaining_ranges, mergeinfo_path,
                                  target_mergeinfo, implicit_mergeinfo,
                                  requested_rangelist,
                                  (revision1 > revision2), entry, pool));
  return SVN_NO_ERROR;
}


static svn_error_t *
get_full_mergeinfo(apr_hash_t **recorded_mergeinfo,
                   apr_hash_t **implicit_mergeinfo,
                   const svn_wc_entry_t *entry,
                   svn_boolean_t *indirect,
                   svn_mergeinfo_inheritance_t inherit,
                   svn_ra_session_t *ra_session,
                   const char *target_wcpath,
                   svn_revnum_t start,
                   svn_revnum_t end,
                   svn_wc_adm_access_t *adm_access,
                   svn_client_ctx_t *ctx,
                   apr_pool_t *pool)
{
  const char *session_url, *url;
  svn_revnum_t target_rev;
  svn_opt_revision_t peg_revision;
  apr_pool_t *sesspool = NULL;

  /* Assert that we have sane input. */
  assert(SVN_IS_VALID_REVNUM(start) 
         && SVN_IS_VALID_REVNUM(end) 
         && (start > end));

  /* First, we get the real mergeinfo. */
  SVN_ERR(svn_client__get_wc_or_repos_mergeinfo(recorded_mergeinfo, entry,
                                                indirect, FALSE, inherit,
                                                ra_session, target_wcpath,
                                                adm_access, ctx, pool));
 
  peg_revision.kind = svn_opt_revision_working;
  SVN_ERR(svn_client__derive_location(&url, &target_rev, target_wcpath,
                                      &peg_revision, ra_session, adm_access,
                                      ctx, pool));
  if (target_rev <= end)
    {
      /* We're asking about a range outside our natural history
         altogether.  That means our implicit mergeinfo is empty. */
      *implicit_mergeinfo = apr_hash_make(pool);
      return SVN_NO_ERROR;
    }

  /* Temporarily point our RA_SESSION at our target URL so we can
     fetch so-called "implicit mergeinfo" (that is, natural history). */
  if (ra_session)
    {
      SVN_ERR(svn_ra_get_session_url(ra_session, &session_url, pool));
      if (strcmp(url, session_url) != 0)
        SVN_ERR(svn_ra_reparent(ra_session, url, pool));
    }
  else
    {
      sesspool = svn_pool_create(pool);
      SVN_ERR(svn_client__open_ra_session_internal(&ra_session, url,
                                                   NULL, NULL, NULL, FALSE, 
                                                   TRUE, ctx, pool));
    }

  /* Our underlying APIs can't yet handle the case where the peg
     revision isn't the youngest of the three revisions.  So we'll
     just verify that the source in the peg revision is related to the
     the source in the youngest requested revision (which is all the
     underlying APIs would do in this case right now anyway). */
  if (target_rev < start)
    {
      const char *start_url;
      svn_opt_revision_t requested, unspec, pegrev, *start_revision;
      unspec.kind = svn_opt_revision_unspecified;
      requested.kind = svn_opt_revision_number;
      requested.value.number = start;
      pegrev.kind = svn_opt_revision_number;
      pegrev.value.number = target_rev;

      SVN_ERR(svn_client__repos_locations(&start_url, &start_revision,
                                          NULL, NULL, ra_session, url,
                                          &pegrev, &requested,
                                          &unspec, ctx, pool));
      /* ### FIXME: Having a low-brain moment.  Shouldn't we check
         that START_URL matches our session URL at this point?  */
      target_rev = start;
    }

  /* Fetch the implicit mergeinfo. */
  peg_revision.kind = svn_opt_revision_number;
  peg_revision.value.number = target_rev;
  SVN_ERR(svn_client__get_history_as_mergeinfo(implicit_mergeinfo, url,
                                               &peg_revision, start, end, 
                                               ra_session, NULL, ctx, pool));

  /* If we created an RA_SESSION above, destroy it.  Otherwise, if
     reparented an existing session, point it back where it was when
     we were called. */
  if (sesspool)
    {
      svn_pool_destroy(sesspool);
    }
  else if (strcmp(url, session_url) != 0)
    {
      SVN_ERR(svn_ra_reparent(ra_session, session_url, pool));
    }

  return SVN_NO_ERROR;
}


/* For each child in CHILDREN_WITH_MERGEINFO, it populates that
   child's remaining_ranges list.  CHILDREN_WITH_MERGEINFO is expected
   to be sorted in depth first order.  All persistent allocations are
   from CHILDREN_WITH_MERGEINFO->pool.

   If HONOR_MERGEINFO is set, this function will actually try to be
   intelligent about populating remaining_ranges list.  Otherwise, it
   will claim that each child has a single remaining range, from
   revision1, to revision2.

   See `MERGEINFO MERGE SOURCE NORMALIZATION' for more requirements
   around the values of URL1, REVISION1, URL2, and REVISION2.
*/
static svn_error_t *
populate_remaining_ranges(apr_array_header_t *children_with_mergeinfo,
                          const char *source_root_url,
                          const char *url1,
                          svn_revnum_t revision1,
                          const char *url2,
                          svn_revnum_t revision2,
                          svn_boolean_t inheritable,
                          svn_boolean_t honor_mergeinfo,
                          svn_ra_session_t *ra_session,
                          const char *parent_merge_src_canon_path,
                          svn_wc_adm_access_t *adm_access,
                          merge_cmd_baton_t *merge_b)
{
  apr_pool_t *iterpool, *pool;
  int merge_target_len = strlen(merge_b->target);
  int i;

  pool = children_with_mergeinfo->pool;
  iterpool = svn_pool_create(pool);

  /* If we aren't honoring mergeinfo, we'll make quick work of this by
     simply adding dummy REVISION1:REVISION2 ranges for all children. */
  if (! honor_mergeinfo)
    {
      for (i = 0; i < children_with_mergeinfo->nelts; i++)
        {
          svn_client__merge_path_t *child =
            APR_ARRAY_IDX(children_with_mergeinfo, i, 
                          svn_client__merge_path_t *);
          svn_merge_range_t *range = apr_pcalloc(pool, sizeof(*range));

          range->start = revision1;
          range->end = revision2;
          range->inheritable = inheritable;

          child->remaining_ranges = 
            apr_array_make(pool, 1, sizeof(svn_merge_range_t *));
          APR_ARRAY_PUSH(child->remaining_ranges, svn_merge_range_t *) = range;
        }
      return SVN_NO_ERROR;
    }

  for (i = 0; i < children_with_mergeinfo->nelts; i++)
    {
      const char *child_repos_path;
      const svn_wc_entry_t *child_entry;
      const char *child_url1, *child_url2;
      apr_hash_t *implicit_mergeinfo;
      svn_client__merge_path_t *child =
        APR_ARRAY_IDX(children_with_mergeinfo, i, svn_client__merge_path_t *);

      /* If the path is absent don't do subtree merge either. */
      if (!child || child->absent)
        continue;

      svn_pool_clear(iterpool);

      if (strlen(child->path) == merge_target_len)
        child_repos_path = "";
      else
        child_repos_path = child->path +
          (merge_target_len ? merge_target_len + 1 : 0);
      child_url1 = svn_path_join(url1, child_repos_path, iterpool);
      child_url2 = svn_path_join(url2, child_repos_path, iterpool);

      SVN_ERR(svn_wc__entry_versioned(&child_entry, child->path, adm_access,
                                      FALSE, iterpool));

      SVN_ERR(get_full_mergeinfo(&(child->pre_merge_mergeinfo), 
                                 &implicit_mergeinfo, child_entry,
                                 &(child->indirect_mergeinfo),
                                 svn_mergeinfo_inherited, NULL, child->path,
                                 MAX(revision1, revision2),
                                 MIN(revision1, revision2),
                                 adm_access, merge_b->ctx, pool));

      SVN_ERR(calculate_remaining_ranges(&(child->remaining_ranges),
                                         source_root_url,
                                         child_url1, revision1,
                                         child_url2, revision2,
                                         inheritable, 
                                         child->pre_merge_mergeinfo,
                                         implicit_mergeinfo,
                                         ra_session, child_entry, merge_b->ctx,
                                         pool));
    }

  /* Take advantage of the depth first ordering,
     i.e first(0th) item is target.*/
  if (children_with_mergeinfo->nelts > 1)
    {
      svn_client__merge_path_t *child =
        APR_ARRAY_IDX(children_with_mergeinfo, 0, svn_client__merge_path_t *);

      if (child->remaining_ranges->nelts == 0)
        {
          svn_merge_range_t *dummy_range = 
            apr_pcalloc(pool, sizeof(*dummy_range));
          dummy_range->start = revision2;
          dummy_range->end = revision2;
          dummy_range->inheritable = inheritable;
          child->remaining_ranges = apr_array_make(pool, 1, 
                                                   sizeof(dummy_range));
          APR_ARRAY_PUSH(child->remaining_ranges, svn_merge_range_t *) =
            dummy_range;
          merge_b->target_has_dummy_merge_range = TRUE;
        }
    }

  svn_pool_destroy(iterpool);
  return SVN_NO_ERROR;
}


/*-----------------------------------------------------------------------*/
\f
/*** Compacting Merge Ranges ***/


/* Callback for qsort() calls which need to sort svn_merge_range_t *.
   Wraps svn_sort_compare_ranges() but first "normalizes" all ranges
   so range->end > range->start. */
static int
compare_merge_ranges(const void *a,
                     const void *b)
{
  /* ### Are all these pointer gymnastics necessary?
     ### There's gotta be a simpler way... */
  svn_merge_range_t *s1 = *((svn_merge_range_t * const *) a);
  svn_merge_range_t *s2 = *((svn_merge_range_t * const *) b);

  /* Convert the svn_merge_range_t to svn_merge_range_t and leverage our
     existing comparison function. */
  svn_merge_range_t r1 = { MIN(s1->start, s1->end),
                           MAX(s1->start, s1->end),
                           TRUE};
  svn_merge_range_t r2 = { MIN(s2->start, s2->end),
                           MAX(s2->start, s2->end),
                           TRUE};
  svn_merge_range_t *r1p = &r1;
  svn_merge_range_t *r2p = &r2;
  return svn_sort_compare_ranges(&r1p, &r2p);
}

/* Another qsort() callback.  Wraps compare_merge_ranges(), but only
   for ranges that share a common "direction", e.g. additive or
   subtractive ranges.  If both ranges are subtractive, the range with
   the lowest (highest absolute) range value is consider the lesser.
   If the direction is not the same, then consider additive merges to
   always be less than subtractive merges. */
static int
compare_merge_ranges2(const void *a,
                      const void *b)
{
  svn_merge_range_t *s1 = *((svn_merge_range_t * const *) a);
  svn_merge_range_t *s2 = *((svn_merge_range_t * const *) b);
  svn_boolean_t s1_reversed = s1->start > s1->end;
  svn_boolean_t s2_reversed = s2->start > s2->end;

  if (s1_reversed && s2_reversed)
    return -(compare_merge_ranges(a, b));
  else if (s1_reversed)
    return 1;
  else if (s2_reversed)
    return -1;
  else
    return compare_merge_ranges(a, b);
}

/* Helper for compact_merge_ranges.  Take *RANGES, an array of
   svn_merge_range_t *, and and remove any redundant ranges, possibly
   removing items from *RANGES.  *RANGES must be sorted per
   compare_merge_ranges() and is guaranteed to be sorted thusly
   upon completion.  All range in RANGES must also be of the same
   "direction" (additive or subtractive). */
static void
remove_redundant_ranges(apr_array_header_t **ranges)
{
  svn_merge_range_t *range_1 = NULL;
  svn_merge_range_t *range_2;
  int i;

  for (i = 0; i < (*ranges)->nelts; i++)
    {
      if (range_1 == NULL)
        {
          range_1 = APR_ARRAY_IDX(*ranges, i, svn_merge_range_t *);
          continue;
        }
      else
        {
          range_2 = APR_ARRAY_IDX(*ranges, i, svn_merge_range_t *);
        }
      if (svn_range_compact(&range_1, &range_2))
        {
          if (!range_2)
            {
              /* Able to compact the two ranges into one.
                 Remove merge_ranges[i] and from array. */
              int j;
              for (j = i; j < (*ranges)->nelts - 1; j++)
                {
                  APR_ARRAY_IDX(*ranges, j, svn_merge_range_t *) =
                    APR_ARRAY_IDX(*ranges, j + 1, svn_merge_range_t *);
                }
              apr_array_pop(*ranges);
              i--; /* Reprocess this element */
            }
        }
    }
}

/* Helper for compact_merge_ranges.  SOURCES is array of svn_merge_range_t *
   sorted per compare_merge_ranges().  Remove any redundant ranges between
   adjacent ranges and store the result in *COMPACTED_RANGES, allocated out
   of pool.  The ranges in *COMPACTED_RANGES will remain sorted as per
   compare_merge_ranges.  Range in RANGES can be of either direction
   (additive and/or subtractive). */
static void
compact_add_sub_ranges(apr_array_header_t **compacted_sources,
                       apr_array_header_t *sources,
                       apr_pool_t *pool)
{
  int i;
  svn_merge_range_t *range_1 = NULL;
  svn_merge_range_t *range_2;
  apr_array_header_t *merge_ranges = apr_array_copy(pool, sources);

  for (i = 0; i < merge_ranges->nelts; i++)
    {
      if (range_1 == NULL)
        {
          range_1 = APR_ARRAY_IDX(merge_ranges, i, svn_merge_range_t *);
          continue;
        }
      else
        {
          range_2 = APR_ARRAY_IDX(merge_ranges, i, svn_merge_range_t *);
        }

      if (svn_range_compact(&range_1, &range_2))
        {
          if (range_1 == NULL && range_2 == NULL) /* ranges cancel each out */
            {
              /* Remove merge_ranges[i] and merge_ranges[i + 1]
                 from the array. */
              int j;
              for (j = i - 1; j < merge_ranges->nelts - 2; j++)
                {
                  APR_ARRAY_IDX(merge_ranges, j, svn_merge_range_t *) =
                    APR_ARRAY_IDX(merge_ranges, j + 2, svn_merge_range_t *);
                }
              apr_array_pop(merge_ranges);
              apr_array_pop(merge_ranges);
              /* Make range_1 the last range processed if one exists. */
              if (i > 1)
                range_1 = APR_ARRAY_IDX(merge_ranges, i - 2,
                                        svn_merge_range_t *);
            }
          else if (!range_2) /* ranges compacted into range_ 1 */
            {
              /* Remove merge_ranges[i] and from array. */
              int j;
              for (j = i; j < merge_ranges->nelts - 1; j++)
                {
                  APR_ARRAY_IDX(merge_ranges, j, svn_merge_range_t *) =
                    APR_ARRAY_IDX(merge_ranges, j + 1, svn_merge_range_t *);
                }
              apr_array_pop(merge_ranges);

              i--; /* Reprocess merge_ranges[i] */
            }
          else /* ranges compacted */
            {
              range_1 = range_2;
            }
        } /* if (svn_range_compact(&range_1, &range_2)) */

    }

  *compacted_sources = merge_ranges;
}

/* SOURCES is array of svn_merge_range_t *sorted per compare_merge_ranges(). */
static svn_error_t *
compact_merge_ranges(apr_array_header_t **compacted_sources_p,
                     apr_array_header_t *merge_ranges,
                     apr_pool_t *pool)
{
  apr_array_header_t *additive_sources =
    apr_array_make(pool, 0, sizeof(svn_merge_range_t *));
  apr_array_header_t *subtractive_sources =
    apr_array_make(pool, 0, sizeof(svn_merge_range_t *));
  apr_array_header_t *compacted_sources;
  int i;

  for (i = 0; i < merge_ranges->nelts; i++)
    {
      svn_merge_range_t *range =
        svn_merge_range_dup(APR_ARRAY_IDX(merge_ranges, i,
                                          svn_merge_range_t *), pool);
      if (range->start > range->end)
        APR_ARRAY_PUSH(subtractive_sources, svn_merge_range_t *) = range;
      else
        APR_ARRAY_PUSH(additive_sources, svn_merge_range_t *) = range;
    }

  qsort(additive_sources->elts, additive_sources->nelts,
        additive_sources->elt_size, compare_merge_ranges);
  remove_redundant_ranges(&additive_sources);
  qsort(subtractive_sources->elts, subtractive_sources->nelts,
        subtractive_sources->elt_size, compare_merge_ranges);
  remove_redundant_ranges(&subtractive_sources);

  for (i = 0; i < subtractive_sources->nelts; i++)
    {
      svn_merge_range_t *range =
        svn_merge_range_dup(APR_ARRAY_IDX(subtractive_sources, i,
                                          svn_merge_range_t *), pool);
      APR_ARRAY_PUSH(additive_sources, svn_merge_range_t *) = range;
    }

  qsort(additive_sources->elts, additive_sources->nelts,
        additive_sources->elt_size, compare_merge_ranges);
  compact_add_sub_ranges(&compacted_sources, additive_sources, pool);
  qsort(compacted_sources->elts, compacted_sources->nelts,
        compacted_sources->elt_size, compare_merge_ranges2);
  *compacted_sources_p = compacted_sources;
  return SVN_NO_ERROR;
}

/*-----------------------------------------------------------------------*/
\f
/*** Other Helper Functions ***/


/* Create mergeinfo describing the merge of RANGE into our target, accounting
   for paths unaffected by the merge due to skips or conflicts from
   NOTIFY_B. For 'immediates' merge it sets an inheritable mergeinfo
   corresponding to current merge on merge target. For 'files' merge it sets
   an inheritable mergeinfo corrsponding to current merge on merged files.
   Note in MERGE_B->OPERATIVE_MERGE if an operative merge
   is discovered.  If TARGET_WCPATH is a directory and it is missing
   an immediate child then TARGET_MISSING_CHILD should be true,
   otherwise it is false.*/
static svn_error_t *
determine_merges_performed(apr_hash_t **merges, const char *target_wcpath,
                           svn_merge_range_t *range,
                           svn_depth_t depth,
                           svn_wc_adm_access_t *adm_access,
                           notification_receiver_baton_t *notify_b,
                           merge_cmd_baton_t *merge_b,
                           apr_pool_t *pool)
{
  apr_array_header_t *rangelist;
  apr_size_t nbr_skips = (notify_b->skipped_paths != NULL ?
                          apr_hash_count(notify_b->skipped_paths) : 0);
  *merges = apr_hash_make(pool);

  /* If there have been no operative merges, then don't calculate anything.
     Just return the empty hash because this whole merge has been a no-op
     and we don't change the mergeinfo in that case (issue #2883). */
   if (notify_b->nbr_operative_notifications > 0)
     merge_b->operative_merge = TRUE;
   else
     return SVN_NO_ERROR;

  rangelist = apr_array_make(pool, 1, sizeof(range));
  APR_ARRAY_PUSH(rangelist, svn_merge_range_t *) = range;
  apr_hash_set(*merges, target_wcpath, APR_HASH_KEY_STRING, rangelist);
  if (nbr_skips > 0)
    {
      apr_hash_index_t *hi;

      /* Override the mergeinfo for child paths which weren't
         actually merged. */
      for (hi = apr_hash_first(NULL, notify_b->skipped_paths); hi;
           hi = apr_hash_next(hi))
        {
          const void *skipped_path;
          apr_hash_this(hi, &skipped_path, NULL, NULL);

          /* Add an empty range list for this path. */
          apr_hash_set(*merges, (const char *) skipped_path,
                       APR_HASH_KEY_STRING,
                       apr_array_make(pool, 0, sizeof(range)));

          if (nbr_skips < notify_b->nbr_notifications)
            /* ### Use RANGELIST as the mergeinfo for all children of
               ### this path which were not also explicitly
               ### skipped? */
            ;
        }
    }
  if ((depth != svn_depth_infinity) && notify_b->merged_paths)
    {
      apr_hash_index_t *hi;
      const void *merged_path;

      for (hi = apr_hash_first(NULL, notify_b->merged_paths); hi;
           hi = apr_hash_next(hi))
        {
          const svn_wc_entry_t *child_entry;
          svn_merge_range_t *child_merge_range;
          apr_array_header_t *rangelist_of_child = NULL;
          apr_hash_this(hi, &merged_path, NULL, NULL);
          child_merge_range = svn_merge_range_dup(range, pool);
          SVN_ERR(svn_wc__entry_versioned(&child_entry,
                                          merged_path,
                                          adm_access, FALSE,
                                          pool));
          if (((child_entry->kind == svn_node_dir)
               && (strcmp(merge_b->target, merged_path) == 0)
               && (depth == svn_depth_immediates))
              || ((child_entry->kind == svn_node_file)
                  && (depth == svn_depth_files)))
            {
              /* Set the explicit inheritable mergeinfo for,
                 1. Merge target directory if depth is immediates.
                 2. If merge is on a file and requested depth is 'files'.
               */
              child_merge_range->inheritable = TRUE;
              rangelist_of_child = apr_array_make(pool, 1, sizeof(range));
            }
          if (rangelist_of_child)
            {
              APR_ARRAY_PUSH(rangelist_of_child, svn_merge_range_t *) =
                child_merge_range;

              apr_hash_set(*merges, (const char *)merged_path,
                           APR_HASH_KEY_STRING, rangelist_of_child);
            }
        }
    }

  return SVN_NO_ERROR;
}

/* Calculate the new mergeinfo for the target tree based on the merge
   info for TARGET_WCPATH and MERGES (a mapping of WC paths to range
   lists), and record it in the WC (at, and possibly below,
   TARGET_WCPATH). */
static svn_error_t *
update_wc_mergeinfo(const char *target_wcpath, const svn_wc_entry_t *entry,
                    const char *repos_rel_path, apr_hash_t *merges,
                    svn_boolean_t is_rollback,
                    svn_wc_adm_access_t *adm_access,
                    svn_client_ctx_t *ctx, apr_pool_t *pool)
{
  apr_pool_t *subpool = svn_pool_create(pool);
  const char *rel_path;
  apr_hash_t *mergeinfo;
  apr_hash_index_t *hi;

  /* Combine the mergeinfo for the revision range just merged into
     the WC with its on-disk mergeinfo. */
  for (hi = apr_hash_first(pool, merges); hi; hi = apr_hash_next(hi))
    {
      const void *key;
      void *value;
      const char *path;
      apr_array_header_t *ranges, *rangelist;
      int len;
      svn_error_t *err;

      svn_pool_clear(subpool);

      apr_hash_this(hi, &key, NULL, &value);
      path = key;
      ranges = value;

      /* As some of the merges may've changed the WC's mergeinfo, get
         a fresh copy before using it to update the WC's mergeinfo. */
      SVN_ERR(svn_client__parse_mergeinfo(&mergeinfo, entry, path, FALSE,
                                          adm_access, ctx, subpool));

      /* If we are attempting to set empty revision range override mergeinfo
         on a path with no explicit mergeinfo, we first need the pristine
         mergeinfo that path inherits. */
      if (mergeinfo == NULL && ranges->nelts == 0)
        {
          svn_boolean_t inherited;
          SVN_ERR(svn_client__get_wc_mergeinfo(&mergeinfo, &inherited, TRUE,
                                               svn_mergeinfo_nearest_ancestor,
                                               entry, path, NULL, NULL,
                                               adm_access, ctx, subpool));
        }

      if (mergeinfo == NULL)
        mergeinfo = apr_hash_make(subpool);

      /* ASSUMPTION: "target_wcpath" is always both a parent and
         prefix of "path". */
      len = strlen(target_wcpath);
      if (len < strlen(path))
        {
          const char *path_relative_to_target = len?(path + len + 1):(path);
          rel_path = apr_pstrcat(subpool, repos_rel_path, "/",
                                 path_relative_to_target, NULL);
        }
      else
        rel_path = repos_rel_path;
      rangelist = apr_hash_get(mergeinfo, rel_path, APR_HASH_KEY_STRING);
      if (rangelist == NULL)
        rangelist = apr_array_make(subpool, 0, sizeof(svn_merge_range_t *));

      if (is_rollback)
        {
          ranges = svn_rangelist_dup(ranges, subpool);
          SVN_ERR(svn_rangelist_reverse(ranges, subpool));
          SVN_ERR(svn_rangelist_remove(&rangelist, ranges, rangelist,
                                       FALSE,
                                       subpool));
        }
      else
        {
          SVN_ERR(svn_rangelist_merge(&rangelist, ranges,
                                      subpool));
        }
      /* Update the mergeinfo by adjusting the path's rangelist. */
      apr_hash_set(mergeinfo, rel_path, APR_HASH_KEY_STRING, rangelist);

      if (is_rollback && apr_hash_count(mergeinfo) == 0)
        mergeinfo = NULL;

      svn_mergeinfo__remove_empty_rangelists(mergeinfo, pool);

      err = svn_client__record_wc_mergeinfo(path, mergeinfo,
                                            adm_access, subpool);

      if (err && err->apr_err == SVN_ERR_ENTRY_NOT_FOUND)
        {
          /* PATH isn't just missing, it's not even versioned as far
             as this working copy knows.  But it was included in
             MERGES, which means that the server knows about it.
             Likely we don't have access to the source due to authz
             restrictions.  For now just clear the error and
             continue...

             ### TODO:  Set non-inheritable mergeinfo on PATH's immediate
             ### parent and normal mergeinfo on PATH's siblings which we
             ### do have access to. */
          svn_error_clear(err);
        }
      else
        SVN_ERR(err);
    }

  svn_pool_destroy(subpool);
  return SVN_NO_ERROR;
}


/* Create and return an error structure appropriate for the unmerged
   revisions range(s). */
static APR_INLINE svn_error_t *
make_merge_conflict_error(const char *target_wcpath,
                          svn_merge_range_t *r,
                          apr_pool_t *pool)
{
  return svn_error_createf
    (SVN_ERR_WC_FOUND_CONFLICT, NULL,
     _("One or more conflicts were produced while merging r%ld:%ld into\n"
       "'%s' --\n"
       "resolve all conflicts and rerun the merge to apply the remaining\n"
       "unmerged revisions"),
     r->start, r->end, svn_path_local_style(target_wcpath, pool));
}

/* Helper for do_directory_merge().

   TARGET_WCPATH is a directory and CHILDREN_WITH_MERGEINFO is filled
   with paths (svn_client__merge_path_t *) arranged in depth first order,
   which have mergeinfo set on them or meet one of the other criteria
   defined in get_mergeinfo_paths().  Remove any paths absent from disk
   or scheduled for deletion from CHILDREN_WITH_MERGEINFO which are equal to
   or are descendants of TARGET_WCPATH by setting those children to NULL.
   Also remove the path from the NOTIFY_B->SKIPPED_PATHS hash. */
static void
remove_absent_children(const char *target_wcpath,
                       apr_array_header_t *children_with_mergeinfo,
                       notification_receiver_baton_t *notify_b)
{
  /* Before we try to override mergeinfo for skipped paths, make sure
     the path isn't absent due to authz restrictions, because there's
     nothing we can do about those. */
  int i;
  for (i = 0; i < children_with_mergeinfo->nelts; i++)
    {
      svn_client__merge_path_t *child =
        APR_ARRAY_IDX(children_with_mergeinfo,
                      i, svn_client__merge_path_t *);
      if (child
          && (child->absent || child->scheduled_for_deletion)
          && svn_path_is_ancestor(target_wcpath, child->path))
        {
          if (notify_b->skipped_paths)
            apr_hash_set(notify_b->skipped_paths, child->path,
                         APR_HASH_KEY_STRING, NULL);
          APR_ARRAY_IDX(children_with_mergeinfo, i,
                        svn_client__merge_path_t *) = NULL;
        }
    }
}

/* Set *HONOR_MERGEINFO and *RECORD_MERGEINFO (if non-NULL)
   appropriately for MERGE_B. */
static APR_INLINE void
mergeinfo_behavior(svn_boolean_t *honor_mergeinfo,
                   svn_boolean_t *record_mergeinfo,
                   merge_cmd_baton_t *merge_b)
{
  if (honor_mergeinfo)
    *honor_mergeinfo = (merge_b->mergeinfo_capable
                        && merge_b->sources_ancestral
                        && merge_b->same_repos
                        && (! merge_b->ignore_ancestry));

  if (record_mergeinfo)
    *record_mergeinfo = (merge_b->mergeinfo_capable
                         && merge_b->sources_ancestral
                         && merge_b->same_repos
                         && (! merge_b->dry_run));
}

/* Sets up the diff editor report and drives it by properly negating
   subtree that could have a conflicting merge history.

   MERGE_B->ra_session1 reflects URL1; MERGE_B->ra_session2 reflects URL2.

   If MERGE_B->sources_ancestral is set, then URL1@REVISION1 must be a
   historical ancestor of URL2@REVISION2, or vice-versa (see
   `MERGEINFO MERGE SOURCE NORMALIZATION' for more requirements around
   the values of URL1, REVISION1, URL2, and REVISION2 in this case).
*/
static svn_error_t *
drive_merge_report_editor(const char *target_wcpath,
                          const char *url1,
                          svn_revnum_t revision1,
                          const char *url2,
                          svn_revnum_t revision2,
                          apr_array_header_t *children_with_mergeinfo,
                          svn_boolean_t is_rollback,
                          svn_depth_t depth,
                          notification_receiver_baton_t *notify_b,
                          svn_wc_adm_access_t *adm_access,
                          const svn_wc_diff_callbacks2_t *callbacks,
                          merge_cmd_baton_t *merge_b,
                          apr_pool_t *pool)
{
  const svn_ra_reporter3_t *reporter;
  const svn_delta_editor_t *diff_editor;
  void *diff_edit_baton;
  void *report_baton;
  svn_revnum_t default_start;
  svn_boolean_t honor_mergeinfo;
  const char *old_sess2_url;

  mergeinfo_behavior(&honor_mergeinfo, NULL, merge_b);

  /* Calculate the default starting revision. */
  default_start = revision1;
  if (honor_mergeinfo)
    {
      if (merge_b->target_has_dummy_merge_range)
        {
          default_start = revision2;
        }
      else if (children_with_mergeinfo && children_with_mergeinfo->nelts)
        {
          svn_client__merge_path_t *child =
            APR_ARRAY_IDX(children_with_mergeinfo, 0, 
                          svn_client__merge_path_t *);
          if (child->remaining_ranges->nelts)
            {
              svn_merge_range_t *range =
                APR_ARRAY_IDX(child->remaining_ranges, 0, 
                              svn_merge_range_t *);
              default_start = range->start;
            }
        }
    }

  /* Temporarily point our second RA session to URL1, too.  We use
     this to request individual file contents. */
  SVN_ERR(svn_client__ensure_ra_session_url(&old_sess2_url, 
                                            merge_b->ra_session2, url1, pool));
  
  /* Get the diff editor and a reporter with which to, ultimately,
     drive it. */
  SVN_ERR(svn_client__get_diff_editor(target_wcpath, adm_access, callbacks,
                                      merge_b, depth, merge_b->dry_run,
                                      merge_b->ra_session2, default_start,
                                      notification_receiver, notify_b,
                                      merge_b->ctx->cancel_func,
                                      merge_b->ctx->cancel_baton,
                                      &diff_editor, &diff_edit_baton,
                                      pool));
  SVN_ERR(svn_ra_do_diff3(merge_b->ra_session1,
                          &reporter, &report_baton, revision2,
                          "", depth, merge_b->ignore_ancestry, 
                          TRUE,  /* text_deltas */
                          url2, diff_editor, diff_edit_baton, pool));

  /* Drive the reporter. */
  SVN_ERR(reporter->set_path(report_baton, "", default_start, depth,
                             FALSE, NULL, pool));
  if (honor_mergeinfo && children_with_mergeinfo)
    {
      /* Describe children with mergeinfo overlapping this merge
         operation such that no repeated diff is retrieved for them from
         the repository. */
      apr_size_t target_wcpath_len = strlen(target_wcpath);
      int i;

      for (i = 1; i < children_with_mergeinfo->nelts; i++)
        {
          svn_merge_range_t *range;
          const char *child_repos_path;
          svn_client__merge_path_t *child =
            APR_ARRAY_IDX(children_with_mergeinfo, i, 
                          svn_client__merge_path_t *);

          if (!child || child->absent || (child->remaining_ranges->nelts == 0))
            continue;

          range = APR_ARRAY_IDX(child->remaining_ranges, 0,
                                svn_merge_range_t *);
          if (range->start == default_start)
            continue;

          child_repos_path = child->path +
            (target_wcpath_len ? target_wcpath_len + 1 : 0);

          if ((is_rollback && (range->start < revision2))
              || (!is_rollback && (range->start > revision2)))
            {
              SVN_ERR(reporter->set_path(report_baton, child_repos_path,
                                         revision2, depth, FALSE, NULL, pool));
            }
          else
            {
              SVN_ERR(reporter->set_path(report_baton, child_repos_path,
                                         range->start, depth, FALSE, 
                                         NULL, pool));
            }
        }
    }
  SVN_ERR(reporter->finish_report(report_baton, pool));

  /* Point the merge baton's second session back where it was. */
  if (old_sess2_url)
    SVN_ERR(svn_ra_reparent(merge_b->ra_session2, old_sess2_url, pool));

  /* Sleep to ensure timestamp integrity. */
  svn_sleep_for_timestamps();

  return SVN_NO_ERROR;
}

/* Return the most inclusive range start revision across all the
   remaining ranges in CHILDREN_WITH_MERGEINFO.  If there are no
   remaining ranges, return SVN_INVALID_REVNUM.  Skip no-op ranges
   on the target (they are probably dummies). */
static svn_revnum_t
get_most_inclusive_start_rev(apr_array_header_t *children_with_mergeinfo,
                             svn_boolean_t is_rollback)
{
  int i;
  svn_revnum_t start_rev = SVN_INVALID_REVNUM;

  for (i = 0; i < children_with_mergeinfo->nelts; i++)
    {
      svn_client__merge_path_t *child =
        APR_ARRAY_IDX(children_with_mergeinfo, i, svn_client__merge_path_t *);
      svn_merge_range_t *range;

      if ((! child) || child->absent)
        continue;
      if (! child->remaining_ranges->nelts)
        continue;
      range = APR_ARRAY_IDX(child->remaining_ranges, 0, svn_merge_range_t *);
      if ((i == 0) && (range->start == range->end))
        continue;
      if ((start_rev == SVN_INVALID_REVNUM)
          || (is_rollback && (range->start > start_rev))
          || ((! is_rollback) && (range->start < start_rev)))
        start_rev = range->start;
    }
  return start_rev;
}

/* Return the youngest qualifying end revision across the first of
   each child in CHILDREN_WITH_MERGEINFO's remaining ranges.  If
   nothing qualifies, return SVN_INVALID_REVNUM. */
static svn_revnum_t
get_youngest_end_rev(apr_array_header_t *children_with_mergeinfo,
                     svn_boolean_t is_rollback)
{
  int i;
  svn_revnum_t end_rev = SVN_INVALID_REVNUM;

  for (i = 0; i < children_with_mergeinfo->nelts; i++)
    {
      svn_client__merge_path_t *child =
        APR_ARRAY_IDX(children_with_mergeinfo, i, svn_client__merge_path_t *);
      if (!child || child->absent)
        continue;
      if (child->remaining_ranges->nelts > 0)
        {
          svn_merge_range_t *range = APR_ARRAY_IDX(child->remaining_ranges, 0,
                                                   svn_merge_range_t *);
          if ((end_rev == SVN_INVALID_REVNUM)
              || (is_rollback && (range->end > end_rev))
              || ((! is_rollback) && (range->end < end_rev)))
            end_rev = range->end;
        }
    }
  return end_rev;
}

/* If first item in each child of CHILDREN_WITH_MERGEINFO's
   remaining_ranges is inclusive of END_REV, Slice the first range in
   to two at END_REV. All the allocations are persistent and allocated
   from POOL. */
static void
slice_remaining_ranges(apr_array_header_t *children_with_mergeinfo,
                       svn_boolean_t is_rollback, svn_revnum_t end_rev,
                       apr_pool_t *pool)
{
  int i;
  for (i = 0; i < children_with_mergeinfo->nelts; i++)
    {
      svn_client__merge_path_t *child =
                                     APR_ARRAY_IDX(children_with_mergeinfo, i,
                                                   svn_client__merge_path_t *);
      if (!child || child->absent)
        continue;
      if (child->remaining_ranges->nelts > 0)
        {
          svn_merge_range_t *range = APR_ARRAY_IDX(child->remaining_ranges, 0,
                                                   svn_merge_range_t *);
          if ((is_rollback && (range->start > end_rev)
               && (range->end < end_rev))
              || (!is_rollback && (range->start < end_rev)
                  && (range->end > end_rev)))
            {
              int j;
              svn_merge_range_t *split_range1, *split_range2;
              apr_array_header_t *orig_remaining_ranges =
                                                     child->remaining_ranges;
              split_range1 = svn_merge_range_dup(range, pool);
              split_range2 = svn_merge_range_dup(range, pool);
              split_range1->end = end_rev;
              split_range2->start = end_rev;
              child->remaining_ranges =
                     apr_array_make(pool, (child->remaining_ranges->nelts + 1),
                                    sizeof(svn_merge_range_t *));
              APR_ARRAY_PUSH(child->remaining_ranges,
                             svn_merge_range_t *) = split_range1;
              APR_ARRAY_PUSH(child->remaining_ranges,
                             svn_merge_range_t *) = split_range2;
              for (j = 1; j < orig_remaining_ranges->nelts; j++)
                {
                  svn_merge_range_t *orig_range =
                                     APR_ARRAY_IDX(orig_remaining_ranges, j,
                                                   svn_merge_range_t *);
                  APR_ARRAY_PUSH(child->remaining_ranges,
                                 svn_merge_range_t *) = orig_range;
                }
            }
        }
    }
}

/* For each child of CHILDREN_WITH_MERGEINFO create a new remaining_ranges
   by removing the first item from the original range list and overwrite the
   original remaining_ranges with this new list.
   All the allocations are persistent from a POOL.
   TODO, we should have remaining_ranges in reverse order to avoid recreating
   the remaining_ranges every time instead of one 'pop' operation.  */
static void
remove_first_range_from_remaining_ranges(
                                apr_array_header_t *children_with_mergeinfo,
                                apr_pool_t *pool)
{
  int i, j;
  for (i = 0; i < children_with_mergeinfo->nelts; i++)
    {
      svn_client__merge_path_t *child =
                                APR_ARRAY_IDX(children_with_mergeinfo, i,
                                              svn_client__merge_path_t *);
      if (!child || child->absent)
        continue;
      if (child->remaining_ranges->nelts > 0)
        {
          apr_array_header_t *orig_remaining_ranges = child->remaining_ranges;
          child->remaining_ranges =
            apr_array_make(pool, (child->remaining_ranges->nelts - 1),
                           sizeof(svn_merge_range_t *));
          for (j = 1; j < orig_remaining_ranges->nelts; j++)
            {
              svn_merge_range_t *range = APR_ARRAY_IDX(orig_remaining_ranges,
                                                       j,
                                                       svn_merge_range_t *);
              APR_ARRAY_PUSH(child->remaining_ranges, svn_merge_range_t *)
                                                                  = range;
            }
        }
    }
}


/* Blindly record the range specified by the user (rather than refining it
   as we do for actual merges) for the merge source URL. */
static svn_error_t *
record_mergeinfo_for_record_only_merge(const char *url,
                                       svn_merge_range_t *range,
                                       const svn_wc_entry_t *entry,
                                       svn_wc_adm_access_t *adm_access,
                                       merge_cmd_baton_t *merge_b,
                                       apr_pool_t *pool)
{
  apr_array_header_t *rangelist;
  const char *rel_path;
  apr_hash_t *target_mergeinfo;
  svn_boolean_t indirect;
  apr_hash_t *merges = apr_hash_make(pool);
  svn_boolean_t is_rollback = (range->start > range->end);
  
  /* Temporarily reparent ra_session to WC target URL. */
  SVN_ERR(svn_ra_reparent(merge_b->ra_session1, entry->url, pool));
  SVN_ERR(svn_client__get_wc_or_repos_mergeinfo(&target_mergeinfo, entry,
                                                &indirect, FALSE,
                                                svn_mergeinfo_inherited,
                                                merge_b->ra_session1,
                                                merge_b->target,
                                                adm_access, merge_b->ctx,
                                                pool));
  /* Reparent ra_session back to URL. */
  SVN_ERR(svn_ra_reparent(merge_b->ra_session1, url, pool));
  SVN_ERR(svn_client__path_relative_to_root(&rel_path, url, NULL, TRUE,
                                            merge_b->ra_session1,
                                            adm_access, pool));
  rangelist = apr_array_make(pool, 1, sizeof(range));
  APR_ARRAY_PUSH(rangelist, svn_merge_range_t *) = range;
  apr_hash_set(merges, merge_b->target, APR_HASH_KEY_STRING, rangelist);

  /* If merge target has indirect mergeinfo set it. */
  if (indirect)
    SVN_ERR(svn_client__record_wc_mergeinfo(merge_b->target, target_mergeinfo,
                                            adm_access, pool));

  return update_wc_mergeinfo(merge_b->target, entry, rel_path, merges,
                             is_rollback, adm_access, merge_b->ctx, pool);
}

/* Marks 'inheritable' RANGE to TARGET_WCPATH by wiping off the
   corresponding 'non-inheritable' RANGE from TARGET_MERGEINFO for the
   merge source REL_PATH.  It does such marking only for same URLs
   from same Repository, not a dry run, target having existing
   mergeinfo(TARGET_MERGEINFO) and target being part of
   CHILDREN_WITH_MERGEINFO. */
static svn_error_t *
mark_mergeinfo_as_inheritable_for_a_range(
                                   apr_hash_t *target_mergeinfo,
                                   svn_boolean_t same_urls,
                                   svn_merge_range_t *range,
                                   const char *rel_path,
                                   const char *target_wcpath,
                                   svn_wc_adm_access_t *adm_access,
                                   merge_cmd_baton_t *merge_b,
                                   apr_array_header_t *children_with_mergeinfo,
                                   int target_index, apr_pool_t *pool)
{
  /* Check if we need to make non-inheritable ranges inheritable. */
  if (target_mergeinfo && same_urls
      && !merge_b->dry_run
      && merge_b->same_repos
      && target_index >= 0)
    {
      svn_client__merge_path_t *merge_path =
        APR_ARRAY_IDX(children_with_mergeinfo,
                      target_index, svn_client__merge_path_t *);

      /* If a path has no missing children, has non-inheritable ranges,
         *and* those non-inheritable ranges intersect with the merge being
         performed (i.e. this is a repeat merge where a previously missing
         child is now present) then those non-inheritable ranges are made
         inheritable. */
      if (merge_path
          && merge_path->has_noninheritable && !merge_path->missing_child)
        {
          svn_boolean_t is_equal;
          apr_hash_t *merges;
          apr_hash_t *inheritable_merges = apr_hash_make(pool);
          apr_array_header_t *inheritable_ranges =
            apr_array_make(pool, 1, sizeof(svn_merge_range_t *));

          APR_ARRAY_PUSH(inheritable_ranges, svn_merge_range_t *) = range;
          apr_hash_set(inheritable_merges, rel_path, APR_HASH_KEY_STRING,
                       inheritable_ranges);

          /* Try to remove any non-inheritable ranges bound by the merge
             being performed. */
          SVN_ERR(svn_mergeinfo_inheritable(&merges, target_mergeinfo,
                                            rel_path, range->start,
                                            range->end, pool));
          /* If any non-inheritable ranges were removed put them back as
             inheritable ranges. */
          SVN_ERR(svn_mergeinfo__equals(&is_equal, merges, target_mergeinfo,
                                        FALSE, pool));
          if (!is_equal)
            {
              SVN_ERR(svn_mergeinfo_merge(merges, inheritable_merges, pool));
              SVN_ERR(svn_client__record_wc_mergeinfo(target_wcpath, merges,
                                                      adm_access, pool));
            }
        }
    }
  return SVN_NO_ERROR;
}

/* For shallow merges record the explicit *indirect* mergeinfo on the

     1. merged files *merged* with a depth 'files'.
     2. merged target directory *merged* with a depth 'immediates'.

   All subtrees which are going to get a 'inheritable merge range'
   because of this 'shallow' merge should have the explicit mergeinfo
   recorded on them. */
static svn_error_t *
record_mergeinfo_on_merged_children(svn_depth_t depth,
                                    svn_wc_adm_access_t *adm_access,
                                    notification_receiver_baton_t *notify_b,
                                    merge_cmd_baton_t *merge_b,
                                    apr_pool_t *pool)
{
  if ((depth != svn_depth_infinity) && notify_b->merged_paths)
    {
      svn_boolean_t indirect_child_mergeinfo = FALSE;
      apr_hash_index_t *hi;
      apr_hash_t *child_target_mergeinfo;
      const void *merged_path;

      for (hi = apr_hash_first(NULL, notify_b->merged_paths); hi;
           hi = apr_hash_next(hi))
        {
          const svn_wc_entry_t *child_entry;
          apr_hash_this(hi, &merged_path, NULL, NULL);
          SVN_ERR(svn_wc__entry_versioned(&child_entry, merged_path,
                                          adm_access, FALSE, pool));
          if (((child_entry->kind == svn_node_dir)
                && (strcmp(merge_b->target, merged_path) == 0)
                && (depth == svn_depth_immediates))
              || ((child_entry->kind == svn_node_file)
                   && (depth == svn_depth_files)))
            {
              /* Set the explicit inheritable mergeinfo for,
                    1. Merge target directory if depth is 'immediates'.
                    2. If merge is on a file and requested depth is 'files'.
               */
              SVN_ERR(svn_client__get_wc_or_repos_mergeinfo
                                      (&child_target_mergeinfo, child_entry,
                                       &indirect_child_mergeinfo,
                                       FALSE, svn_mergeinfo_inherited,
                                       merge_b->ra_session1, merged_path,
                                       adm_access, merge_b->ctx, pool));
              if (indirect_child_mergeinfo)
                SVN_ERR(svn_client__record_wc_mergeinfo(merged_path,
                                                        child_target_mergeinfo,
                                                        adm_access, pool));
            }
        }
    }
  return SVN_NO_ERROR;
}


/* Get REVISION of the file at URL.  SOURCE is a path that refers to that
   file's entry in the working copy, or NULL if we don't have one.  Return in
   *FILENAME the name of a file containing the file contents, in *PROPS a hash
   containing the properties and in *REV the revision.  All allocation occurs
   in POOL. */
static svn_error_t *
single_file_merge_get_file(const char **filename,
                           svn_ra_session_t *ra_session,
                           apr_hash_t **props,
                           svn_revnum_t rev,
                           const char *wc_target,
                           apr_pool_t *pool)
{
  apr_file_t *fp;
  svn_stream_t *stream;

  /* ### Create this temporary file under .svn/tmp/ instead of next to
     ### the working file.*/
  SVN_ERR(svn_io_open_unique_file2(&fp, filename,
                                   wc_target, ".tmp",
                                   svn_io_file_del_none, pool));
  stream = svn_stream_from_aprfile2(fp, FALSE, pool);
  SVN_ERR(svn_ra_get_file(ra_session, "", rev,
                          stream, NULL, props, pool));
  SVN_ERR(svn_stream_close(stream));

  return SVN_NO_ERROR;
}


/* Send a notification specific to a single-file merge. */
static APR_INLINE void
single_file_merge_notify(void *notify_baton, const char *target_wcpath,
                         svn_wc_notify_action_t action,
                         svn_wc_notify_state_t text_state,
                         svn_wc_notify_state_t prop_state, apr_pool_t *pool)
{
  svn_wc_notify_t *notify = svn_wc_create_notify(target_wcpath, action, pool);
  notify->kind = svn_node_file;
  notify->content_state = text_state;
  notify->prop_state = prop_state;
  if (notify->content_state == svn_wc_notify_state_missing)
    notify->action = svn_wc_notify_skip;
  notification_receiver(notify_baton, notify, pool);
}


/* A baton for get_mergeinfo_walk_cb. */
struct get_mergeinfo_walk_baton
{
  /* Access for the tree being walked. */
  svn_wc_adm_access_t *base_access;
  /* Array of paths that have explicit mergeinfo and/or are switched. */
  apr_array_header_t *children_with_mergeinfo;
  /* Merge source canonical path. */
  const char* merge_src_canon_path;
  
  /* Information on the merge cascaded from do_directory_merge() */
  const char* merge_target_path;
  const char *source_root_url;
  const char* url1;
  const char* url2;
  svn_revnum_t revision1;
  svn_revnum_t revision2;
  
  /* merge depth requested. */
  svn_depth_t depth;
  
  /* RA session and client context cascaded from do_directory_merge() */
  svn_ra_session_t *ra_session;
  svn_client_ctx_t *ctx;
};


/* svn_wc_entry_callbacks2_t found_entry() callback for get_mergeinfo_paths.

   Given PATH, its corresponding ENTRY, and WB, where WB is the WALK_BATON
   of type "struct get_mergeinfo_walk_baton *":  If PATH is switched,
   has explicit working svn:mergeinfo from a corresponding merge source, is
   missing a child due to a sparse checkout, is absent from disk, or is
   scheduled for deletion, then create a svn_client__merge_path_t *
   representing *PATH, allocated in WB->CHILDREN_WITH_MERGEINFO->POOL, and
   push it onto the WB->CHILDREN_WITH_MERGEINFO array. */
static svn_error_t *
get_mergeinfo_walk_cb(const char *path,
                      const svn_wc_entry_t *entry,
                      void *walk_baton,
                      apr_pool_t *pool)
{
  struct get_mergeinfo_walk_baton *wb = walk_baton;
  const svn_string_t *propval;
  apr_hash_t *mergehash;
  svn_boolean_t switched = FALSE;
  svn_boolean_t has_mergeinfo_from_merge_src = FALSE;
  svn_boolean_t path_is_merge_target =
    !svn_path_compare_paths(path, wb->merge_target_path);
  const char *parent_path = svn_path_dirname(path, pool);

  /* We're going to receive dirents twice;  we want to ignore the
     first one (where it's a child of a parent dir), and only use
     the second one (where we're looking at THIS_DIR).  The exception
     is absent dirs, these only come through once, so continue. */
  if ((entry->kind == svn_node_dir)
      && (strcmp(entry->name, SVN_WC_ENTRY_THIS_DIR) != 0)
      && !entry->absent)
    return SVN_NO_ERROR;

  /* Ignore the entry if it does not exist at the time of interest. */
  if (entry->deleted)
    return SVN_NO_ERROR;

  if (entry->absent || entry->schedule == svn_wc_schedule_delete)
    {
      propval = NULL;
      switched = FALSE;
    }
  else
    {
      SVN_ERR(svn_wc_prop_get(&propval, SVN_PROP_MERGEINFO, path,
                              wb->base_access, pool));
      /* We always include the merge target regardless of its mergeinfo.
         So we don't need to check that PATH's mergeinfo corresponds to
         the merge source. */
      if (propval && !path_is_merge_target)
        {
          svn_stringbuf_t *merge_src_child_path =
            svn_stringbuf_create(wb->merge_src_canon_path, pool);

          /* When the merge target is '' or '.' WB->MERGE_TARGET_PATH is
             an empty string and PATH will always be relative.  In this case
             we can safely combine WB->MERGE_SRC_CANON_PATH and PATH with
             svn_path_add_compent() which will supply the missing '/' separator.

             Otherwise WB->MERGE_TARGET_PATH is relative or absolute and
             we remove the common root component between WB->MERGE_TARGET_PATH
             and PATH from PATH before combining it with
             WB->MERGE_SRC_CANON_PATH.  The +1 is required because if we are
             here that means WB->MERGE_TARGET_PATH is a proper ancestor of
             PATH and we must skip the path separator -- svn_path_add_compent()
             will add missing separators, but won't remove existing ones -- to
             avoid a merge_src_child_path with "//" in it. */
          if (strlen(wb->merge_target_path))
            svn_path_add_component(merge_src_child_path,
                                   path + strlen(wb->merge_target_path) + 1);
          else
            svn_path_add_component(merge_src_child_path,
                                   path);
          SVN_ERR(svn_mergeinfo_parse(&mergehash, propval->data, pool));
          if (apr_hash_get(mergehash, merge_src_child_path->data,
                           APR_HASH_KEY_STRING))
            {
              /* The easy way: PATH already has mergeinfo
                 from this source... */
              has_mergeinfo_from_merge_src = TRUE;
            }
          else
            {
              /* ...the slightly harder way: See if PATH exists in the
                 merge source at the revisions being merged. If it doesn't
                 exist there is no way this subtree can be affected by the
                 merge so we can safely leave it, and its mergeinfo, alone. */
              svn_error_t *err;
              const char *original_ra_url;
              const char *mergeinfo_url =
                svn_path_join(wb->source_root_url,
                              /* Skip leading '/' or join won't work. */
                              ++(merge_src_child_path->data),
                              pool);
              svn_opt_revision_t *start_revision, *end_revision;
              const char *start_url, *end_url;
              svn_opt_revision_t peg_rev, rev1_opt, rev2_opt;
                      
              peg_rev.value.number = wb->revision1 < wb->revision2
                ? wb->revision2 : wb->revision1;
              peg_rev.kind = svn_opt_revision_number;
              
              rev1_opt.kind = svn_opt_revision_number;
              rev1_opt.value.number = wb->revision1;
                  
              rev2_opt.kind = svn_opt_revision_number;
              rev2_opt.value.number = wb->revision2;
              
              /* Instead of passing NULL to svn_client__repos_locations() and
                 causing another session to open, reparent WB->RA_SESSION
                 and use that. */
              SVN_ERR(svn_ra_get_session_url(wb->ra_session, &original_ra_url,
                                             pool));
              SVN_ERR(svn_ra_reparent(wb->ra_session, mergeinfo_url, pool));

              /* Does PATH exist in the merge source? */
              err = svn_client__repos_locations(&start_url, &start_revision,
                                                &end_url, &end_revision,
                                                wb->ra_session, mergeinfo_url,
                                                &peg_rev, &rev1_opt, &rev2_opt,
                                                wb->ctx, pool);
              if (err)
                {
                  /* We might see any of these errors depending on the RA
                     access method, but they all mean that PATH doesn't exist
                     in the merge source.
                     
                     ### TODO: Make svn_client__repos_locations() more
                     ###       consistent in the error it returns(?)
                     */
                  if (err->apr_err == SVN_ERR_FS_NOT_FOUND
                      || err->apr_err == SVN_ERR_RA_DAV_PATH_NOT_FOUND
                      || err->apr_err == SVN_ERR_CLIENT_UNRELATED_RESOURCES)
                    svn_error_clear(err);
                  else
                    return err;
                }

              /* Reparent the WB->RA_SESSION to its original URL. */
              SVN_ERR(svn_ra_reparent(wb->ra_session, original_ra_url, pool));

              if (!err) /* PATH does exist in the merge source*/
                {
                  if (propval->len > 0)
                    {
                      has_mergeinfo_from_merge_src = TRUE;
                    }
                  else /* Handle the special case of empty mergeinfo */
                    {
                      /* WC->WC copies (and moves) can't contact the server
                         and so leave empty mergefino on the copy target to
                         prevent it from erroneously inheriting the incorrect
                         mergeinfo from the repos (if any exists) during a
                         merge.  Reverse merges may also leave empty mergeinfo
                         on a path so this state is not exclusive to WC->WC
                         copies.
                         
                         Because the WC->WC copy behavior is a safety net,
                         the empty mergeinfo on a path *may* not actually
                         override anything.  In the case where this is true,
                         we don't need to treat PATH as a subtree with
                         intersecting mergeinfo, we can simply merge into
                         PATH's parent (which may be the merge target
                         itself)...

                         ...So, if we find empty mergeinfo on PATH see if
                         PATH has any ancestor with mergeinfo. */
                      apr_hash_t *overidden_mergeinfo;
                      svn_boolean_t indirect;
                      SVN_ERR(svn_client__get_wc_or_repos_mergeinfo(
                        &overidden_mergeinfo, entry,
                        &indirect, FALSE, svn_mergeinfo_nearest_ancestor,
                        wb->ra_session, path, wb->base_access, wb->ctx,
                        pool));
                      if (indirect)
                        {
                          /* Ok, we found empty mergeinfo which overrides some
                             parent with mergeinfo.  Time for one final
                             optimization: If the mergeinfo overridden is
                             *also* empty, then we can perform some preemptive
                             elision right now and remove the empty mergeinfo
                             from PATH.  Even if the overriden parent is in
                             the repository it's ok, since the merge target
                             *always* gets mergeinfo set (though it may
                             elide).*/
                          svn_boolean_t equal_mergeinfo;
                          SVN_ERR(svn_mergeinfo__equals(&equal_mergeinfo,
                                                        mergehash,
                                                        overidden_mergeinfo,
                                                        FALSE, pool));
                          if (equal_mergeinfo)
                            SVN_ERR(svn_client__record_wc_mergeinfo(
                              path, NULL, wb->base_access, pool));
                          else
                            /* The empty mergeinfo on PATH really means
                               something.  Merge this subtree separately. */
                            has_mergeinfo_from_merge_src = TRUE;
                        }
                    }
                } /* (!err) */
              start_url = NULL;
            } /* the slightly harder way */
        }
      /* Regardless of whether PATH has explicit mergeinfo or not, we must
         determine if PATH is switched.  This is so get_mergeinfo_paths()
         can later tweak PATH's parent to reflect a missing child (implying it
         needs non-inheritable mergeinfo ranges) and PATH's siblings so they
         get their own complete set of mergeinfo. */
      SVN_ERR(svn_wc__path_switched(path, &switched, entry, pool));
    }

  /* Store PATHs with explict mergeinfo, which are switched, are missing
     children due to a sparse checkout, are scheduled for deletion are absent
     from the WC, and/or are first level sub directories relative to merge
     target if depth is immediates. */
  if (path_is_merge_target
      || has_mergeinfo_from_merge_src
      || entry->schedule == svn_wc_schedule_delete
      || switched
      || entry->depth == svn_depth_empty
      || entry->depth == svn_depth_files
      || entry->absent
      || ((wb->depth == svn_depth_immediates) &&
          (entry->kind == svn_node_dir) &&
          (strcmp(parent_path, path) != 0) &&
          (strcmp(parent_path, wb->merge_target_path) == 0)))
    {
      svn_client__merge_path_t *child =
        apr_pcalloc(wb->children_with_mergeinfo->pool, sizeof(*child));
      child->path = apr_pstrdup(wb->children_with_mergeinfo->pool, path);
      child->missing_child = (entry->depth == svn_depth_empty
                              || entry->depth == svn_depth_files
                              || ((wb->depth == svn_depth_immediates) &&
                                  (entry->kind == svn_node_dir) &&
                                  (strcmp(parent_path,
                                          wb->merge_target_path) == 0)))
                              ? TRUE : FALSE;
      child->switched = switched;
      child->absent = entry->absent;
      child->scheduled_for_deletion =
        entry->schedule == svn_wc_schedule_delete ? TRUE : FALSE;
      if (propval)
        {
          if (strstr(propval->data, SVN_MERGEINFO_NONINHERITABLE_STR))
            child->has_noninheritable = TRUE;
          child->propval =
            svn_string_create(propval->data,
                              wb->children_with_mergeinfo->pool);
        }

      /* A little trickery: If PATH doesn't have any mergeinfo or has
         only inheritable mergeinfo, we still describe it as having
         non-inheritable mergeinfo if it is missing a child.  Why?  Because
         the mergeinfo we'll add to PATH as a result of the merge will need
         to be non-inheritable (since PATH is missing children) and doing
         this now allows get_mergeinfo_paths() to properly account for PATH's
         other children. */
      if (!child->has_noninheritable
          && (entry->depth == svn_depth_empty
              || entry->depth == svn_depth_files))
      child->has_noninheritable = TRUE;

      APR_ARRAY_PUSH(wb->children_with_mergeinfo,
                     svn_client__merge_path_t *) = child;
    }

  return SVN_NO_ERROR;
}

/* svn_wc_entry_callbacks2_t handle_error() callback for
   get_mergeinfo_paths().

   Squelch ERR by returning SVN_NO_ERROR if ERR is caused by a missing
   path (i.e. SVN_ERR_WC_PATH_NOT_FOUND) or an unversioned path
   (i.e. SVN_ERR_WC_NOT_LOCKED). */
static svn_error_t *
get_mergeinfo_error_handler(const char *path,
                            svn_error_t *err,
                            void *walk_baton,
                            apr_pool_t *pool)
{
  svn_error_t *root_err = svn_error_root_cause(err);
  if (root_err == SVN_NO_ERROR)
    return err;

  switch (root_err->apr_err)
    {
    case SVN_ERR_WC_PATH_NOT_FOUND:
    case SVN_ERR_WC_NOT_LOCKED:
      svn_error_clear(err);
      return SVN_NO_ERROR;

    default:
      return err;
    }
}

/* Helper for get_mergeinfo_paths()

   CHILDREN_WITH_MERGEINFO is a depth first sorted array filled with
   svn_client__merge_path_t *.  Starting at the element in
   CHILDREN_WITH_MERGEINFO located at START_INDEX look for that
   element's child/parent (as indicated by LOOKING_FOR_CHILD) named
   PATH. If the child/parent is found, set *CHILD_OR_PARENT to that
   element and return the index at which if was found.  If the
   child/parent is not found set *CHILD_OR_PARENT to NULL and return
   the index at which it should be inserted. */
static int
find_child_or_parent(apr_array_header_t *children_with_mergeinfo,
                     svn_client__merge_path_t **child_or_parent,
                     const char *path,
                     svn_boolean_t looking_for_child,
                     int start_index,
                     apr_pool_t *pool)
{
  int j = 0;
  *child_or_parent = NULL;

  /* If possible, search forwards in the depth first sorted array
     to find a child PATH or backwards to find a parent PATH. */
  if (start_index >= 0 && start_index < children_with_mergeinfo->nelts)
    {
      for (j = looking_for_child ? start_index + 1 : start_index;
           looking_for_child ? j < children_with_mergeinfo->nelts : j >= 0;
           j = looking_for_child ? j + 1 : j - 1)
        {
          /* If this potential child is neither the child we are looking for
             or another one of PARENT's children then CHILD_PATH doesn't
             exist in CHILDREN_WITH_MERGEINFO. */
          svn_client__merge_path_t *potential_child_or_parent =
            APR_ARRAY_IDX(children_with_mergeinfo, j,
                          svn_client__merge_path_t *);
          int cmp = svn_path_compare_paths(path,
                                           potential_child_or_parent->path);
          if (cmp == 0)
            {
              /* Found child or parent. */
              *child_or_parent = potential_child_or_parent;
              break;
            }
          else if ((looking_for_child && cmp < 0)
                   || (!looking_for_child && cmp > 0))
            {
              /* PATH doesn't exist, but found where it should be inserted. */
              if (!looking_for_child)
                j++;
              break;
            }
          else if (!looking_for_child && j == 0)
            {
              /* Looking for a parent but are at start of the array so we know
                 where to insert the parent. */
              break;
            }
          /* else we are looking for a child but found one of its
             siblings...keep looking. */
        }
    }
  return j;
}

/* Helper for get_mergeinfo_paths()

   CHILDREN_WITH_MERGEINFO is a depth first sorted array filled with
   svn_client__merge_path_t *.  Insert INSERT_ELEMENT into the
   CHILDREN_WITH_MERGEINFO array at index INSERT_INDEX. */
static void
insert_child_to_merge(apr_array_header_t *children_with_mergeinfo,
                      svn_client__merge_path_t *insert_element,
                      int insert_index)
{
  if (insert_index == children_with_mergeinfo->nelts)
    {
      APR_ARRAY_PUSH(children_with_mergeinfo,
                     svn_client__merge_path_t *) = insert_element;
    }
  else
    {
      /* Copy the last element of CHILDREN_WITH_MERGEINFO and add it to the
         end of the array. */
      int j;
      svn_client__merge_path_t *curr =
        APR_ARRAY_IDX(children_with_mergeinfo,
                      children_with_mergeinfo->nelts - 1,
                      svn_client__merge_path_t *);
      svn_client__merge_path_t *curr_copy =
        apr_palloc(children_with_mergeinfo->pool, sizeof(*curr_copy));

      *curr_copy = *curr;
      APR_ARRAY_PUSH(children_with_mergeinfo,
                     svn_client__merge_path_t *) = curr_copy;

      /* Move all elements from INSERT_INDEX to the end of the array forward
         one spot then insert the new element. */
      for (j = children_with_mergeinfo->nelts - 2; j >= insert_index; j--)
        {
          svn_client__merge_path_t *prev;
          curr = APR_ARRAY_IDX(children_with_mergeinfo, j,
                               svn_client__merge_path_t *);
          if (j == insert_index)
            *curr = *insert_element;
          else
            {
              prev = APR_ARRAY_IDX(children_with_mergeinfo, j - 1,
                                   svn_client__merge_path_t *);
              *curr = *prev;
            }
        }
    }
}

/* Helper for get_mergeinfo_paths()'s qsort() call. */
static int
compare_merge_path_t_as_paths(const void *a,
                              const void *b)
{
  svn_client__merge_path_t *child1 = *((svn_client__merge_path_t * const *) a);
  svn_client__merge_path_t *child2 = *((svn_client__merge_path_t * const *) b);

  return svn_path_compare_paths(child1->path, child2->path);
}

/* Helper for get_mergeinfo_paths().  If CHILD->PATH is switched,
   absent, or scheduled for deletion make sure its parent is marked
   as missing a child.  Start looking up for parent from *CURR_INDEX
   in CHILDREN_WITH_MERGEINFO.  Create the parent and insert it into
   CHILDREN_WITH_MERGEINFO if necessary (and increment *CURR_INDEX
   so that caller don't process the inserted element).  Also ensure
   that CHILD->PATH's siblings which are not already present in
   CHILDREN_WITH_MERGEINFO are also added to the array. Use POOL for
   all temporary allocations. */
static svn_error_t *
insert_parent_and_sibs_of_sw_absent_del_entry(
                                   apr_array_header_t *children_with_mergeinfo,
                                   merge_cmd_baton_t *merge_cmd_baton,
                                   int *curr_index,
                                   svn_client__merge_path_t *child,
                                   svn_wc_adm_access_t *adm_access,
                                   apr_pool_t *pool)
{
  svn_client__merge_path_t *parent;
  const char *parent_path = svn_path_dirname(child->path, pool);
  apr_hash_t *entries;
  apr_hash_index_t *hi;
  svn_wc_adm_access_t *parent_access;
  int insert_index, parent_index;

  if (!(child->absent
        || child->scheduled_for_deletion
          || (child->switched
              && strcmp(merge_cmd_baton->target, child->path) != 0)))
    return SVN_NO_ERROR;

  parent_index = find_child_or_parent(children_with_mergeinfo, &parent,
                                      parent_path, FALSE, *curr_index, pool);
  if (parent)
    {
      parent->missing_child = TRUE;
    }
  else
    {
      /* Create a new element to insert into CHILDREN_WITH_MERGEINFO. */
      parent = apr_pcalloc(children_with_mergeinfo->pool, sizeof(*parent));
      parent->path = apr_pstrdup(children_with_mergeinfo->pool, parent_path);
      parent->missing_child = TRUE;
      /* Insert PARENT into CHILDREN_WITH_MERGEINFO. */
      insert_child_to_merge(children_with_mergeinfo, parent, parent_index);
      /* Increment for loop index so we don't process the inserted element. */
      (*curr_index)++;
    } /*(parent == NULL) */

  /* Add all of PARENT's non-missing children that are not already present.*/
  SVN_ERR(svn_wc_adm_probe_try3(&parent_access, adm_access, parent->path,
                                TRUE, -1, merge_cmd_baton->ctx->cancel_func,
                                merge_cmd_baton->ctx->cancel_baton, pool));
  SVN_ERR(svn_wc_entries_read(&entries, parent_access, FALSE, pool));
  for (hi = apr_hash_first(pool, entries); hi; hi = apr_hash_next(hi))
    {
      const void *key;
      svn_client__merge_path_t *sibling_of_missing;
      const char *child_path;

      apr_hash_this(hi, &key, NULL, NULL);

      if (strcmp(key, SVN_WC_ENTRY_THIS_DIR) == 0)
        continue;

      /* Does this child already exist in CHILDREN_WITH_MERGEINFO? */
      child_path = svn_path_join(parent->path, key, pool);
      insert_index = find_child_or_parent(children_with_mergeinfo,
                                          &sibling_of_missing, child_path,
                                          TRUE, parent_index, pool);
      /* Create the missing child and insert it into CHILDREN_WITH_MERGEINFO.*/
      if (!sibling_of_missing)
        {
          sibling_of_missing = apr_pcalloc(children_with_mergeinfo->pool,
                                           sizeof(*sibling_of_missing));
          sibling_of_missing->path = apr_pstrdup(children_with_mergeinfo->pool,
                                                 child_path);
          insert_child_to_merge(children_with_mergeinfo, sibling_of_missing,
                                insert_index);
        }
    }
  return SVN_NO_ERROR;
}

/* Helper for do_directory_merge()

   Perform a depth first walk of the working copy tree rooted at
   MERGE_CMD_BATON->TARGET (with the corresponding ENTRY).  Create an
   svn_client__merge_path_t * for any path which meets one or more of the
   following criteria:

     1) Path has working svn:mergeinfo from corresponding merge source.
     2) Path is switched.
     3) Path has no mergeinfo of it's own but it's parent has mergeinfo with
        non-inheritable ranges (in this case the function will actually set
        override mergeinfo on the path if this isn't a dry-run and the merge
        is between differences in the same repository).
     4) Path has an immediate child (or children) missing from the WC because
        the child is switched or absent from the WC, or due to a sparse
        checkout.
     5) Path has a sibling (or siblings) missing from the WC because the
        sibling is switched, absent, schduled for deletion, or missing due to
        a sparse checkout.
     6) Path is absent from disk due to an authz restriction.
     7) Path is scheduled for deletion.
     8) Path is equal to MERGE_CMD_BATON->TARGET.

   Store the svn_client__merge_path_t *'s in *CHILDREN_WITH_MERGEINFO in
   depth-first order based on the svn_client__merge_path_t *s path member as
   sorted by svn_path_compare_paths().

   Note: Since the walk is rooted at MERGE_CMD_BATON->TARGET, the latter is
   guaranteed to be in *CHILDREN_WITH_MERGEINFO and due to the depth-first
   ordering it is guaranteed to be the first element in
   *CHILDREN_WITH_MERGEINFO.

   Cascade MERGE_SRC_CANON_PATH. */
static svn_error_t *
get_mergeinfo_paths(apr_array_header_t *children_with_mergeinfo,
                    merge_cmd_baton_t *merge_cmd_baton,
                    const char* merge_src_canon_path,
                    const svn_wc_entry_t *entry,
                    const char *source_root_url,
                    const char *url1,
                    const char *url2,
                    svn_revnum_t revision1,
                    svn_revnum_t revision2,
                    svn_ra_session_t *ra_session,
                    svn_wc_adm_access_t *adm_access,
                    svn_client_ctx_t *ctx,
                    svn_depth_t depth,
                    apr_pool_t *pool)
{
  int i;
  apr_pool_t *iterpool;
  static const svn_wc_entry_callbacks2_t walk_callbacks =
    { get_mergeinfo_walk_cb, get_mergeinfo_error_handler };
  struct get_mergeinfo_walk_baton wb =
    { adm_access, children_with_mergeinfo,
      merge_src_canon_path, merge_cmd_baton->target, source_root_url,
      url1, url2, revision1, revision2, depth, ra_session, ctx };

  /* Cover cases 1), 2), 6), and 8) by walking the WC to get all paths which
     have mergeinfo and/or are switched or are absent from disk or is the
     target of the merge. */
  if (entry->kind == svn_node_file)
    SVN_ERR(walk_callbacks.found_entry(merge_cmd_baton->target, entry, &wb,
                                       pool));
  else
    SVN_ERR(svn_wc_walk_entries3(merge_cmd_baton->target, adm_access,
                                 &walk_callbacks, &wb, depth, TRUE,
                                 merge_cmd_baton->ctx->cancel_func,
                                 merge_cmd_baton->ctx->cancel_baton,
                                 pool));

  /* CHILDREN_WITH_MERGEINFO must be in depth first order, but
     svn_wc_walk_entries3() relies on svn_wc_entries_read() which means the
     paths at a given directory level are not in any particular order.  Also,
     we may need to add elements to the array to cover case 3) through 5) from
     the docstring.  If so, it is more efficient to find and insert these
     paths if the sibling paths are in a guaranteed depth-first order.  For
     the first reason we sort the array, for the second reason we do it now
     rather than at the end of this function. */
  qsort(children_with_mergeinfo->elts,
        children_with_mergeinfo->nelts,
        children_with_mergeinfo->elt_size,
        compare_merge_path_t_as_paths);

  iterpool = svn_pool_create(pool);
  for (i = 0; i < children_with_mergeinfo->nelts; i++)
    {
      int insert_index;
      svn_client__merge_path_t *child =
        APR_ARRAY_IDX(children_with_mergeinfo, i, svn_client__merge_path_t *);
      svn_pool_clear(iterpool);

      /* Case 3) Where merging to a path with a switched child the path gets
         non-inheritable mergeinfo for the merge range performed and the child
         gets it's own set of mergeinfo.  If the switched child later
         "returns", e.g. a switched path is unswitched, the child may not have
         any explicit mergeinfo.  If the initial merge is repeated we don't
         want to repeat the merge for the path, but we do want to repeat it
         for the previously switched child.  To ensure this we check if all
         of CHILD's non-missing children have explicit mergeinfo (they should
         already be present in CHILDREN_WITH_MERGEINFO if they do).  If not,
         add the children without mergeinfo to CHILDREN_WITH_MERGEINFO so
         do_directory_merge() will merge them independently.

         But that's not enough!  Since do_directory_merge() performs
         the merges on the paths in CHILDREN_WITH_MERGEINFO in a depth first
         manner it will merge the previously switched path's parent first.  As
         part of this merge it will update the parent's previously
         non-inheritable mergeinfo and make it inheritable (since it notices
         the path has no missing children), then when
         do_directory_merge() finally merges the previously missing
         child it needs to get mergeinfo from the child's nearest ancestor,
         but since do_directory_merge() already tweaked that
         mergeinfo, removing the non-inheritable flag, it appears that the
         child already has been merged to.  To prevent this we set override
         mergeinfo on the child now, before any merging is done, so it has
         explicit mergeinfo that reflects only CHILD's inheritable
         mergeinfo. */

      if (child->has_noninheritable)
        {
          apr_hash_t *entries;
          apr_hash_index_t *hi;
          svn_wc_adm_access_t *child_access;
          SVN_ERR(svn_wc_adm_probe_try3(&child_access, adm_access,
                                        child->path, TRUE, -1,
                                        merge_cmd_baton->ctx->cancel_func,
                                        merge_cmd_baton->ctx->cancel_baton,
                                        iterpool));
          SVN_ERR(svn_wc_entries_read(&entries, child_access, FALSE,
                                      iterpool));
          for (hi = apr_hash_first(iterpool, entries); hi;
               hi = apr_hash_next(hi))
            {
              const void *key;
              svn_client__merge_path_t *child_of_noninheritable;
              const char *child_path;

              apr_hash_this(hi, &key, NULL, NULL);

              if (strcmp(key, SVN_WC_ENTRY_THIS_DIR) == 0)
                continue;

              /* Does this child already exist in CHILDREN_WITH_MERGEINFO?  If
                 not, create it and insert it into CHILDREN_WITH_MERGEINFO and
                 set override mergeinfo on it. */
              child_path = svn_path_join(child->path, key, iterpool);
              insert_index = find_child_or_parent(children_with_mergeinfo,
                                                  &child_of_noninheritable,
                                                  child_path, TRUE, i,
                                                  iterpool);
              if (!child_of_noninheritable)
                {
                  child_of_noninheritable =
                    apr_pcalloc(children_with_mergeinfo->pool,
                                sizeof(*child_of_noninheritable));
                  child_of_noninheritable->path =
                    apr_pstrdup(children_with_mergeinfo->pool, child_path);
                  insert_child_to_merge(children_with_mergeinfo,
                                        child_of_noninheritable,
                                        insert_index);
                  if (!merge_cmd_baton->dry_run
                      && merge_cmd_baton->same_repos)
                    {
                      svn_boolean_t inherited;
                      apr_hash_t *mergeinfo;
                      merge_cmd_baton->override_set = TRUE;
                      SVN_ERR(svn_client__get_wc_mergeinfo
                              (&mergeinfo, &inherited, FALSE,
                               svn_mergeinfo_nearest_ancestor,
                               entry, child_of_noninheritable->path,
                               merge_cmd_baton->target, NULL, adm_access,
                               merge_cmd_baton->ctx, iterpool));
                      SVN_ERR(svn_client__record_wc_mergeinfo(
                        child_of_noninheritable->path, mergeinfo, adm_access,
                        iterpool));
                    }
                }
            }
        }
      /* Case 4, 5, and 7 are handled by the following function. */
      SVN_ERR(insert_parent_and_sibs_of_sw_absent_del_entry(
        children_with_mergeinfo, merge_cmd_baton, &i, child,
        adm_access, iterpool));
    } /* i < children_with_mergeinfo->nelts */

  svn_pool_destroy(iterpool);
  return SVN_NO_ERROR;
}


/*-----------------------------------------------------------------------*/
\f
/*** Merge Source Normalization ***/

typedef struct merge_source_t
{
  /* "left" side URL and revision (inclusive iff youngest) */
  const char *url1;
  svn_revnum_t rev1;

  /* "right" side URL and revision (inclusive iff youngest) */
  const char *url2;
  svn_revnum_t rev2;

} merge_source_t;

/* qsort-compatible sort routine, rating merge_source_t * objects to
   be in descending (youngest-to-oldest) order based on their ->rev1
   component. */
static int
compare_merge_source_ts(const void *a,
                        const void *b)
{
  svn_revnum_t a_rev = ((const merge_source_t *)a)->rev1;
  svn_revnum_t b_rev = ((const merge_source_t *)b)->rev1;
  if (a_rev == b_rev)
    return 0;
  return a_rev < b_rev ? 1 : -1;
}

/* Set MERGE_SOURCE_TS_P to a list of merge sources generated by
   slicing history location SEGMENTS with a given requested merge
   RANGE.  Use SOURCE_ROOT_URL for full source URL calculation.  */
static svn_error_t *
combine_range_with_segments(apr_array_header_t **merge_source_ts_p,
                            svn_merge_range_t *range,
                            apr_array_header_t *segments,
                            const char *source_root_url,
                            apr_pool_t *pool)
{
  apr_array_header_t *merge_source_ts =
    apr_array_make(pool, 1, sizeof(merge_source_t *));
  svn_revnum_t minrev = MIN(range->start, range->end) + 1;
  svn_revnum_t maxrev = MAX(range->start, range->end);
  svn_boolean_t subtractive = (range->start > range->end);
  int i;

  for (i = 0; i < segments->nelts; i++)
    {
      svn_location_segment_t *segment =
        APR_ARRAY_IDX(segments, i, svn_location_segment_t *);
      merge_source_t *merge_source;
      const char *path1 = NULL;
      svn_revnum_t rev1;

      /* If this segment doesn't overlap our range at all, or
         represents a gap, ignore it. */
      if ((segment->range_end < minrev)
          || (segment->range_start > maxrev)
          || (! segment->path))
        continue;

      /* If our range spans a segment boundary, we have to point our
         merge_source_t's path1 to the path of the immediately older
         segment, else it points to the same location as its path2.  */
      rev1 = MAX(segment->range_start, minrev) - 1;
      if (minrev <= segment->range_start)
        {
          if (i > 0)
            {
              path1 = (APR_ARRAY_IDX(segments, i - 1,
                                     svn_location_segment_t *))->path;
            }
          /* If we've backed PATH1 up into a segment gap, let's back
             it up further still to the segment before the gap.  We'll
             have to adjust rev1, too. */
          if ((! path1) && (i > 1))
            {
              path1 = (APR_ARRAY_IDX(segments, i - 2,
                                     svn_location_segment_t *))->path;
              rev1 = (APR_ARRAY_IDX(segments, i - 2,
                                    svn_location_segment_t *))->range_end;
            }
        }
      else
        {
          path1 = apr_pstrdup(pool, segment->path);
        }

      /* If we don't have two valid paths, we won't know what to do
         when merging.  This could happen if someone requested a merge
         where the source didn't exist in a particular revision or
         something.  The merge code would probably bomb out anyway, so
         we'll just *not* create a merge source in this case. */
      if (! (path1 && segment->path))
        continue;

      /* Build our merge source structure. */
      merge_source = apr_pcalloc(pool, sizeof(*merge_source));
      merge_source->url1 = svn_path_join(source_root_url, 
                                         svn_path_uri_encode(path1, 
                                                             pool), pool);
      merge_source->url2 = svn_path_join(source_root_url, 
                                         svn_path_uri_encode(segment->path, 
                                                             pool), pool);
      merge_source->rev1 = rev1;
      merge_source->rev2 = MIN(segment->range_end, maxrev);

      /* If this is subtractive, reverse the whole calculation. */
      if (subtractive)
        {
          svn_revnum_t tmprev = merge_source->rev1;
          const char *tmpurl = merge_source->url1;
          merge_source->rev1 = merge_source->rev2;
          merge_source->url1 = merge_source->url2;
          merge_source->rev2 = tmprev;
          merge_source->url2 = tmpurl;
        }

      APR_ARRAY_PUSH(merge_source_ts, merge_source_t *) = merge_source;
    }

  /* If this was a subtractive merge, and we created more than one
     merge source, we need to reverse the sort ordering of our sources. */
  if (subtractive && (merge_source_ts->nelts > 1))
    qsort(merge_source_ts->elts, merge_source_ts->nelts,
          merge_source_ts->elt_size, compare_merge_source_ts);

  *merge_source_ts_p = merge_source_ts;
  return SVN_NO_ERROR;
}

/* Set *MERGE_SOURCES to an array of merge_source_t * objects, each
   holding the paths and revisions needed to fully describe a range of
   requested merges.  Determine the requested merges by examining
   SOURCE (and its associated URL, SOURCE_URL) and PEG_REVISION (which
   specifies the line of history from which merges will be pulled) and
   RANGES_TO_MERGE (a list of svn_opt_revision_range_t's which provide
   revision ranges).

   If PEG_REVISION is unspecified, treat that it as HEAD.

   SOURCE_ROOT_URL is the root URL of the source repository.

   Use RA_SESSION -- whose session URL matches SOURCE_URL -- to answer
   historical questions.

   CTX is a client context baton.

   Use POOL for all allocation.

   See `MERGEINFO MERGE SOURCE NORMALIZATION' for more on the
   background of this function.
*/
static svn_error_t *
normalize_merge_sources(apr_array_header_t **merge_sources_p,
                        const char *source,
                        const char *source_url,
                        const char *source_root_url,
                        const svn_opt_revision_t *peg_revision,
                        const apr_array_header_t *ranges_to_merge,
                        svn_ra_session_t *ra_session,
                        svn_client_ctx_t *ctx,
                        apr_pool_t *pool)
{
  svn_revnum_t youngest_rev = SVN_INVALID_REVNUM;
  svn_revnum_t peg_revnum;
  svn_revnum_t oldest_requested = SVN_INVALID_REVNUM;
  svn_revnum_t youngest_requested = SVN_INVALID_REVNUM;
  svn_opt_revision_t youngest_opt_rev;
  apr_array_header_t *merge_range_ts, *segments;
  apr_pool_t *subpool;
  int i;
  youngest_opt_rev.kind = svn_opt_revision_head;

  /* Initialize our return variable. */
  *merge_sources_p = apr_array_make(pool, 1, sizeof(merge_source_t *));

  /* Resolve our PEG_REVISION to a real number. */
  SVN_ERR(svn_client__get_revision_number(&peg_revnum, &youngest_rev,
                                          ra_session, peg_revision,
                                          source, pool));
  if (! SVN_IS_VALID_REVNUM(peg_revnum))
    return svn_error_create(SVN_ERR_CLIENT_BAD_REVISION, NULL, NULL);

  /* Create a list to hold svn_merge_range_t's. */
  merge_range_ts = apr_array_make(pool, ranges_to_merge->nelts,
                                  sizeof(svn_merge_range_t *));

  subpool = svn_pool_create(pool);
  for (i = 0; i < ranges_to_merge->nelts; i++)
    {
      svn_revnum_t range_start_rev, range_end_rev;
      svn_opt_revision_t *range_start =
        &((APR_ARRAY_IDX(ranges_to_merge, i,
                         svn_opt_revision_range_t *))->start);
      svn_opt_revision_t *range_end =
        &((APR_ARRAY_IDX(ranges_to_merge, i,
                         svn_opt_revision_range_t *))->end);

      svn_pool_clear(subpool);

      /* Resolve revisions to real numbers, validating as we go. */
      if ((range_start->kind == svn_opt_revision_unspecified)
          || (range_end->kind == svn_opt_revision_unspecified))
        return svn_error_create(SVN_ERR_CLIENT_BAD_REVISION, NULL,
                                _("Not all required revisions are specified"));
      SVN_ERR(svn_client__get_revision_number(&range_start_rev, &youngest_rev,
                                              ra_session, range_start,
                                              source, subpool));
      SVN_ERR(svn_client__get_revision_number(&range_end_rev, &youngest_rev,
                                              ra_session, range_end,
                                              source, subpool));

      /* If this isn't a no-op range... */
      if (range_start_rev != range_end_rev)
        {
          /* ...then create an svn_merge_range_t object for it. */
          svn_merge_range_t *range = apr_pcalloc(pool, sizeof(*range));
          range->start = range_start_rev;
          range->end = range_end_rev;
          range->inheritable = TRUE;

          /* Add our merge range to our list thereof. */
          APR_ARRAY_PUSH(merge_range_ts, svn_merge_range_t *) = range;
        }
    }

  /* Okay.  We have a list of svn_merge_range_t's.  Now, we need to
     compact that list to remove redundances and such. */
  SVN_ERR(compact_merge_ranges(&merge_range_ts, merge_range_ts, pool));

  /* No compacted ranges to merge?  No problem. */
  if (merge_range_ts->nelts == 0)
    return SVN_NO_ERROR;

  /* Find the extremes of the revisions across our set of ranges. */
  for (i = 0; i < merge_range_ts->nelts; i++)
    {
      svn_merge_range_t *range =
        APR_ARRAY_IDX(merge_range_ts, i, svn_merge_range_t *);
      svn_revnum_t minrev = MIN(range->start, range->end);
      svn_revnum_t maxrev = MAX(range->start, range->end);

      /* Keep a running tally of the oldest and youngest requested
         revisions. */
      if ((! SVN_IS_VALID_REVNUM(oldest_requested))
          || (minrev < oldest_requested))
        oldest_requested = minrev;
      if ((! SVN_IS_VALID_REVNUM(youngest_requested))
          || (maxrev > youngest_requested))
        youngest_requested = maxrev;
    }

  /* ### FIXME:  Our underlying APIs can't yet handle the case where
     the peg revision isn't the youngest of the three revisions.  So
     we'll just verify that the source in the peg revision is related
     to the the source in the youngest requested revision (which is
     all the underlying APIs would do in this case right now anyway). */
  if (peg_revnum < youngest_requested)
    {
      const char *start_url;
      svn_opt_revision_t requested, unspec, pegrev, *start_revision;
      unspec.kind = svn_opt_revision_unspecified;
      requested.kind = svn_opt_revision_number;
      requested.value.number = youngest_requested;
      pegrev.kind = svn_opt_revision_number;
      pegrev.value.number = peg_revnum;

      SVN_ERR(svn_client__repos_locations(&start_url, &start_revision,
                                          NULL, NULL,
                                          ra_session, source_url,
                                          &pegrev, &requested,
                                          &unspec, ctx, pool));
      peg_revnum = youngest_requested;
    }

  /* Fetch the locations for our merge range span. */
  SVN_ERR(svn_client__repos_location_segments(&segments,
                                              ra_session, "",
                                              peg_revnum,
                                              youngest_requested,
                                              oldest_requested,
                                              ctx, pool));

  /* For each range in our requested range set, try to determine the
     path(s) associated with that range.  */
  for (i = 0; i < merge_range_ts->nelts; i++)
    {
      svn_merge_range_t *range =
        APR_ARRAY_IDX(merge_range_ts, i, svn_merge_range_t *);
      apr_array_header_t *merge_sources;
      int j;

      /* Copy the resulting merge sources into master list thereof. */
      SVN_ERR(combine_range_with_segments(&merge_sources, range,
                                          segments, source_root_url, pool));
      for (j = 0; j < merge_sources->nelts; j++)
        {
          APR_ARRAY_PUSH(*merge_sources_p, merge_source_t *) =
            APR_ARRAY_IDX(merge_sources, j, merge_source_t *);
        }
    }

  return SVN_NO_ERROR;
}


/*-----------------------------------------------------------------------*/
\f
/*** Merge Workhorse Functions ***/

/* The single-file, simplified version of do_directory_merge(), which see for
   parameter descriptions. 

   Additional parameters:

   If SOURCES_RELATED is set, the "left" and "right" sides of the
   merge source are historically related (ancestors, uncles, second
   cousins thrice removed, etc...).  (This is used to simulate the
   history checks that the repository logic does in the directory case.)  
*/
static svn_error_t *
do_file_merge(const char *url1,
              svn_revnum_t revision1,
              const char *url2,
              svn_revnum_t revision2,
              const char *target_wcpath,
              svn_boolean_t sources_related,
              svn_wc_adm_access_t *adm_access,
              notification_receiver_baton_t *notify_b,
              merge_cmd_baton_t *merge_b,
              apr_pool_t *pool)
{
  svn_error_t *err = SVN_NO_ERROR;
  apr_hash_t *props1, *props2;
  const char *tmpfile1, *tmpfile2;
  const char *mimetype1, *mimetype2;
  svn_string_t *pval;
  apr_array_header_t *propchanges, *remaining_ranges;
  svn_wc_notify_state_t prop_state = svn_wc_notify_state_unknown;
  svn_wc_notify_state_t text_state = svn_wc_notify_state_unknown;
  svn_client_ctx_t *ctx = merge_b->ctx;
  const char *mergeinfo_path;
  svn_merge_range_t range;
  apr_hash_t *target_mergeinfo;
  const svn_wc_entry_t *entry;
  int i;
  svn_boolean_t indirect = FALSE;
  apr_pool_t *subpool;
  svn_boolean_t is_rollback = (revision1 > revision2);
  const char *primary_url = is_rollback ? url1 : url2;
  svn_boolean_t honor_mergeinfo, record_mergeinfo;

  mergeinfo_behavior(&honor_mergeinfo, &record_mergeinfo, merge_b);

  /* Note that this is a single-file merge. */
  notify_b->is_single_file_merge = TRUE;

  /* Ensure that the adm_access we're playing with is our TARGET_WCPATH's
     parent, as required by some of underlying helper functions. */
  SVN_ERR(svn_wc_adm_probe_try3(&adm_access, adm_access, target_wcpath,
                                TRUE, -1, merge_b->ctx->cancel_func,
                                merge_b->ctx->cancel_baton,
                                pool));

  SVN_ERR(svn_wc__entry_versioned(&entry, target_wcpath, adm_access, FALSE,
                                  pool));

  range.start = revision1;
  range.end = revision2;
  range.inheritable = TRUE;
  if (honor_mergeinfo)
    {
      const char *source_root_url;
      apr_hash_t *implicit_mergeinfo;

      /* Fetch mergeinfo (temporarily reparenting ra_session1 to
         working copy target URL). */
      SVN_ERR(svn_ra_reparent(merge_b->ra_session1, entry->url, pool));
      SVN_ERR(get_full_mergeinfo(&target_mergeinfo, &implicit_mergeinfo, entry,
                                 &indirect, svn_mergeinfo_inherited,
                                 merge_b->ra_session1, target_wcpath, 
                                 MAX(revision1, revision2),
                                 MIN(revision1, revision2),
                                 adm_access, ctx, pool));
      SVN_ERR(svn_ra_reparent(merge_b->ra_session1, url1, pool));

      /* Calculate remaining merges. */
      SVN_ERR(svn_ra_get_repos_root(merge_b->ra_session1,
                                    &source_root_url, pool));
      SVN_ERR(svn_client__path_relative_to_root(&mergeinfo_path, primary_url,
                                                source_root_url, TRUE, NULL,
                                                NULL, pool));
      SVN_ERR(calculate_remaining_ranges(&remaining_ranges, source_root_url,
                                         url1, revision1, url2, revision2,
                                         TRUE, target_mergeinfo, 
                                         implicit_mergeinfo,
                                         merge_b->ra_session1,
                                         entry, ctx, pool));
    }
  else
    {
      remaining_ranges = apr_array_make(pool, 1, sizeof(&range));
      APR_ARRAY_PUSH(remaining_ranges, svn_merge_range_t *) = &range;
    }

  subpool = svn_pool_create(pool);

  for (i = 0; i < remaining_ranges->nelts; i++)
    {
      svn_wc_notify_t *n;

      /* When using this merge range, account for the exclusivity of
         its low value (which is indicated by this operation being a
         merge vs. revert). */
      svn_merge_range_t *r = APR_ARRAY_IDX(remaining_ranges, i,
                                           svn_merge_range_t *);

      svn_pool_clear(subpool);

      n = svn_wc_create_notify(target_wcpath,
                               svn_wc_notify_merge_begin,
                               subpool);
      if (merge_b->sources_ancestral)
        n->merge_range = r;
      notification_receiver(notify_b, n, subpool);

      /* While we currently don't allow it, in theory we could be
         fetching two fulltexts from two different repositories here. */
      SVN_ERR(single_file_merge_get_file(&tmpfile1, merge_b->ra_session1,
                                         &props1, r->start, target_wcpath,
                                         subpool));
      SVN_ERR(single_file_merge_get_file(&tmpfile2, merge_b->ra_session2,
                                         &props2, r->end, target_wcpath,
                                         subpool));

      /* Discover any svn:mime-type values in the proplists */
      pval = apr_hash_get(props1, SVN_PROP_MIME_TYPE,
                          strlen(SVN_PROP_MIME_TYPE));
      mimetype1 = pval ? pval->data : NULL;

      pval = apr_hash_get(props2, SVN_PROP_MIME_TYPE,
                          strlen(SVN_PROP_MIME_TYPE));
      mimetype2 = pval ? pval->data : NULL;

      /* Deduce property diffs. */
      SVN_ERR(svn_prop_diffs(&propchanges, props2, props1, subpool));

      /* If we aren't ignoring ancestry, then we've already done
         ancestry relatedness checks.  If we are ignoring ancestry, or
         our sources are known to be related, then we can do
         text-n-props merge; otherwise, we have to do a delete-n-add
         merge.  */
      if (! (merge_b->ignore_ancestry || sources_related))
        {
          /* Delete... */
          SVN_ERR(merge_file_deleted(adm_access,
                                     &text_state,
                                     target_wcpath,
                                     NULL,
                                     NULL,
                                     mimetype1, mimetype2,
                                     props1,
                                     merge_b));
          single_file_merge_notify(notify_b, target_wcpath,
                                   svn_wc_notify_update_delete, text_state,
                                   svn_wc_notify_state_unknown, subpool);

          /* ...plus add... */
          SVN_ERR(merge_file_added(adm_access,
                                   &text_state, &prop_state,
                                   target_wcpath,
                                   tmpfile1,
                                   tmpfile2,
                                   r->start,
                                   r->end,
                                   mimetype1, mimetype2,
                                   propchanges, props1,
                                   merge_b));
          single_file_merge_notify(notify_b, target_wcpath,
                                   svn_wc_notify_update_add, text_state,
                                   prop_state, subpool);
          /* ... equals replace. */
        }
      else
        {
          SVN_ERR(merge_file_changed(adm_access,
                                     &text_state, &prop_state,
                                     target_wcpath,
                                     tmpfile1,
                                     tmpfile2,
                                     r->start,
                                     r->end,
                                     mimetype1, mimetype2,
                                     propchanges, props1,
                                     merge_b));
          single_file_merge_notify(notify_b, target_wcpath,
                                   svn_wc_notify_update_update, text_state,
                                   prop_state, subpool);
        }

      /* Ignore if temporary file not found. It may have been renamed. */
      /* (This is where we complain about missing Lisp, or better yet,
         Python...) */
      err = svn_io_remove_file(tmpfile1, subpool);
      if (err && ! APR_STATUS_IS_ENOENT(err->apr_err))
        return err;
      svn_error_clear(err);
      err = SVN_NO_ERROR;
      err = svn_io_remove_file(tmpfile2, subpool);
      if (err && ! APR_STATUS_IS_ENOENT(err->apr_err))
        return err;
      svn_error_clear(err);
      err = SVN_NO_ERROR;

      if (i < remaining_ranges->nelts - 1 &&
          is_path_conflicted_by_merge(merge_b))
        {
          err = make_merge_conflict_error(target_wcpath, r, pool);
          break;
        }
    }

  /* Record updated WC mergeinfo to account for our new merges, minus
     any unresolved conflicts and skips. */
  if (record_mergeinfo && remaining_ranges->nelts)
    {
      apr_hash_t *merges;
      SVN_ERR(determine_merges_performed(&merges, target_wcpath,
                                         &range, svn_depth_infinity,
                                         adm_access, notify_b, merge_b,
                                         subpool));
      /* If this whole merge was simply a no-op merge to a file then
         we don't touch the local mergeinfo. */
      if (merge_b->operative_merge)
        {
          /* If merge target has indirect mergeinfo set it before
             recording the first merge range. */
          if (indirect)
            SVN_ERR(svn_client__record_wc_mergeinfo(target_wcpath,
                                                    target_mergeinfo,
                                                    adm_access, subpool));
          
          SVN_ERR(update_wc_mergeinfo(target_wcpath, entry, mergeinfo_path,
                                      merges, is_rollback, adm_access,
                                      ctx, subpool));
        }
    }

  svn_pool_destroy(subpool);

  /* Sleep to ensure timestamp integrity. */
  svn_sleep_for_timestamps();

  return err;
}


/* Perform a merge of changes between URL1@REVISION1 and
   URL2@REVISION2, applied to the children of PARENT_ENTRY.  URL1,
   URL2, and PARENT_ENTRY all represent directories -- for the single
   file case, the caller should use do_file_merge().

   If MERGE_B->sources_ancestral is set, then URL1@REVISION1 must be a
   historical ancestor of URL2@REVISION2, or vice-versa (see
   `MERGEINFO MERGE SOURCE NORMALIZATION' for more requirements around
   the values of URL1, REVISION1, URL2, and REVISION2 in this case).

   Handle DEPTH as documented for svn_client_merge3().

   CHILDREN_WITH_MERGEINFO may contain child paths (svn_client__merge_path_t *)
   which are switched or which have mergeinfo which differs from that of the
   merge target root (ignored if empty or NULL).  CHILDREN_WITH_MERGEINFO
   list should have entries sorted in depth first order as mandated by the
   reporter API. Because of this, we drive the diff editor in such a way that
   it avoids merging child paths when a merge is driven for their parent path.

   CHILDREN_WITH_MERGEINFO may contain TARGET_WCPATH (which may be
   MERGE_B->TARGET), in that case TARGET_INDEX is the array index for
   TARGET_WCPATH, otherwise it should be set to a negative value.

   NOTE: This is a wrapper around drive_merge_report_editor() which
   handles the complexities inherent to situations where a given
   directory's children may have intersecting merges (because they
   meet one or more of the criteria described in get_mergeinfo_paths()).
*/
static svn_error_t *
do_directory_merge(const char *url1,
                   svn_revnum_t revision1,
                   const char *url2,
                   svn_revnum_t revision2,
                   const svn_wc_entry_t *parent_entry,
                   svn_wc_adm_access_t *adm_access,
                   svn_depth_t depth,
                   notification_receiver_baton_t *notify_b,
                   merge_cmd_baton_t *merge_b,
                   apr_pool_t *pool)
{
  svn_error_t *err = SVN_NO_ERROR;
  apr_array_header_t *children_with_mergeinfo;
  int merge_target_len = strlen(merge_b->target);
  int i;
  svn_merge_range_t range;
  svn_ra_session_t *ra_session;
  svn_boolean_t inheritable;
  apr_pool_t *iterpool;
  const char *target_wcpath = svn_wc_adm_access_path(adm_access);
  svn_client__merge_path_t *target_merge_path;
  svn_boolean_t is_rollback = (revision1 > revision2);
  const char *primary_url = is_rollback ? url1 : url2;
  const char *source_root_url, *mergeinfo_path;
  svn_boolean_t honor_mergeinfo, record_mergeinfo;
  svn_boolean_t same_urls = (strcmp(url1, url2) == 0);

  mergeinfo_behavior(&honor_mergeinfo, &record_mergeinfo, merge_b);

  /* Initialize CHILDREN_WITH_MERGEINFO. */
  children_with_mergeinfo =
    apr_array_make(pool, 0, sizeof(svn_client__merge_path_t *));
  notify_b->children_with_mergeinfo = children_with_mergeinfo;

  /* If our merge sources aren't related to each other, or don't come
     from the same repository as our target, mergeinfo is meaningless
     and we can skip right to the business of merging changes!  We'll
     just drop a dummy item into CHILDREN_WITH_MERGEINFO if the merge
     sources are related.  */
  if (! (merge_b->sources_ancestral && merge_b->same_repos))
    {
      if (merge_b->sources_ancestral)
        {
          svn_client__merge_path_t *item = apr_pcalloc(pool, sizeof(*item));
          svn_merge_range_t *itemrange = apr_pcalloc(pool, sizeof(*itemrange));
          apr_array_header_t *remaining_ranges =
            apr_array_make(pool, 1, sizeof(svn_merge_range_t *));

          itemrange->start = revision1;
          itemrange->end = revision2;
          itemrange->inheritable = TRUE;
          APR_ARRAY_PUSH(remaining_ranges, svn_merge_range_t *) = itemrange;

          item->path = apr_pstrdup(pool, target_wcpath);
          item->remaining_ranges = remaining_ranges;
          APR_ARRAY_PUSH(children_with_mergeinfo, 
                         svn_client__merge_path_t *) = item;
        }
      return drive_merge_report_editor(target_wcpath,
                                       url1, revision1, url2, revision2,
                                       NULL, is_rollback, depth, notify_b, 
                                       adm_access, &merge_callbacks, 
                                       merge_b, pool);
    }

  /*** If we get here, we're dealing with related sources from the
       same repository as the target -- merge tracking might be
       happenin'! ***/

  /* Point our RA_SESSION to the URL of our youngest merge source side. */
  ra_session = is_rollback ? merge_b->ra_session1 : merge_b->ra_session2;

  /* Fill CHILDREN_WITH_MERGEINFO with child paths (const
     svn_client__merge_path_t *) which might have intersecting merges
     because they meet one or more of the criteria described in
     get_mergeinfo_paths(). Here the paths are arranged in a depth
     first order. */
  SVN_ERR(svn_ra_get_repos_root(ra_session, &source_root_url, pool));
  SVN_ERR(svn_client__path_relative_to_root(&mergeinfo_path, primary_url,
                                            source_root_url, TRUE, NULL,
                                            NULL, pool));
  SVN_ERR(get_mergeinfo_paths(children_with_mergeinfo, merge_b,
                              mergeinfo_path, parent_entry, source_root_url,
                              url1, url2, revision1, revision2,
                              ra_session, adm_access,
                              merge_b->ctx, depth, pool));

  /* The first item from the CHILDREN_WITH_MERGEINFO is the target
     thanks to depth-first ordering. */
  target_merge_path = APR_ARRAY_IDX(children_with_mergeinfo, 0,
                                    svn_client__merge_path_t *);
  merge_b->target_missing_child = target_merge_path->missing_child;
  inheritable = ((! merge_b->target_missing_child)
                 && ((depth == svn_depth_infinity)
                     || (depth == svn_depth_immediates)));

  /* If we are honoring mergeinfo, then for each item in
     CHILDREN_WITH_MERGEINFO, we need to calculate what needs to be
     merged, and then merge it.  Otherwise, we just merge what we were
     asked to merge across the whole tree.  */
  SVN_ERR(populate_remaining_ranges(children_with_mergeinfo, 
                                    source_root_url,
                                    url1, revision1, url2, revision2,
                                    inheritable, honor_mergeinfo,
                                    ra_session, mergeinfo_path,
                                    adm_access, merge_b));

  if (honor_mergeinfo)
    {
      svn_revnum_t start_rev, end_rev;

      /* From the remaining ranges of each item in
         CHILDREN_WITH_MERGEINFO, pick the most inclusive start and
         end revisions. */
      start_rev = get_most_inclusive_start_rev(children_with_mergeinfo,
                                               is_rollback);
      if (start_rev == SVN_INVALID_REVNUM)
        start_rev = revision1;

      end_rev = get_youngest_end_rev(children_with_mergeinfo, is_rollback);

      /* Build a range which describes our most inclusive merge. */
      range.start = start_rev;
      range.end = revision2;
      range.inheritable = inheritable;

      /* While END_REV is valid, do the following:

         1. slice each remaining ranges around this 'end_rev'.
         2. starting with START_REV, call
            drive_merge_report_editor() on MERGE_B->target for 
            start_rev:end_rev.
         3. remove the first item from each remaining range.
         4. set START_REV=END_REV and pick the next END_REV.
         5. lather, rinse, repeat.
      */
      iterpool = svn_pool_create(pool);
      while (end_rev != SVN_INVALID_REVNUM)
        {
          svn_revnum_t next_end_rev;
          const char *real_url1 = url1, *real_url2 = url2;
          const char *old_sess1_url = NULL, *old_sess2_url = NULL;

          svn_pool_clear(iterpool);

          /* Use persistent pool while playing with remaining_ranges. */
          slice_remaining_ranges(children_with_mergeinfo, is_rollback,
                                 end_rev, pool);
          notify_b->cur_ancestor_index = -1;

          /* URL1@REVISION1 is a real location; URL2@REVISION2 is a
             real location -- that much we know (thanks to the merge
             source normalization code).  But for revisions between
             them, the URLs might differ.  Here are the rules:

               * If URL1 == URL2, then all URLs between REVISION1 and
                 REVISION2 also match URL1/URL2.

               * If URL1 != URL2, then:

                   * If REVISION1 < REVISION2, only REVISION1 maps to
                     URL1.  The revisions between REVISION1+1 and
                     REVISION2 (inclusive) map to URL2.

                   * If REVISION1 > REVISION2, Only REVISION2 maps to
                     URL2.  The revisions between REVISION1 and
                     REVISION2+1 (inclusive) map to URL1.
               
             We need to adjust our URLs accordingly, here.
          */
          if (! same_urls)
            {
              if (is_rollback && (end_rev != revision2))
                {
                  real_url2 = url1;
                  SVN_ERR(svn_client__ensure_ra_session_url
                          (&old_sess2_url, merge_b->ra_session2,
                           real_url2, iterpool));
                }
              if ((! is_rollback) && (start_rev != revision1))
                {
                  real_url1 = url2;
                  SVN_ERR(svn_client__ensure_ra_session_url
                          (&old_sess1_url, merge_b->ra_session1,
                           real_url1, iterpool));
                }
            }
          SVN_ERR(drive_merge_report_editor(merge_b->target,
                                            real_url1, start_rev, real_url2, 
                                            end_rev, children_with_mergeinfo,
                                            is_rollback,
                                            depth, notify_b, adm_access,
                                            &merge_callbacks, merge_b,
                                            iterpool));
          if (old_sess1_url)
            SVN_ERR(svn_ra_reparent(merge_b->ra_session1, 
                                    old_sess1_url, iterpool));
          if (old_sess2_url)
            SVN_ERR(svn_ra_reparent(merge_b->ra_session2, 
                                    old_sess2_url, iterpool));

          /* Prepare for the next iteration (if any). */
          remove_first_range_from_remaining_ranges(children_with_mergeinfo, 
                                                   pool);
          next_end_rev = get_youngest_end_rev(children_with_mergeinfo, 
                                              is_rollback);
          if ((next_end_rev != SVN_INVALID_REVNUM)
              && is_path_conflicted_by_merge(merge_b))
            {
              svn_merge_range_t conflicted_range;
              conflicted_range.start = start_rev;
              conflicted_range.end = end_rev;
              err = make_merge_conflict_error(merge_b->target,
                                              &conflicted_range, pool);
              range.end = end_rev;
              break;
            }
          start_rev = end_rev;
          end_rev = next_end_rev;
        }
      svn_pool_destroy(iterpool);
    }
  else
    {
      /* Build a range which describes our most inclusive merge. */
      range.start = revision1;
      range.end = revision2;
      range.inheritable = inheritable;

      SVN_ERR(drive_merge_report_editor(merge_b->target,
                                        url1, revision1, url2, revision2,
                                        NULL, is_rollback, 
                                        depth, notify_b, adm_access, 
                                        &merge_callbacks, merge_b, 
                                        pool));
    }

  /* Record mergeinfo where appropriate.

     NOTE: any paths in CHILDREN_WITH_MERGEINFO which were switched
     but had no explicit working mergeinfo at the start of the call,
     will have some at the end of it if merge is not a no-op merge.
  */
  iterpool = svn_pool_create(pool);
  if (record_mergeinfo)
    {
      /* Update the WC mergeinfo here to account for our new
         merges, minus any unresolved conflicts and skips. */
      apr_hash_t *merges;

      /* Remove absent children at or under TARGET_WCPATH from
         NOTIFY_B->SKIPPED_PATHS and CHILDREN_WITH_MERGEINFO before we
         calculate the merges performed. */
      remove_absent_children(merge_b->target,
                             children_with_mergeinfo, notify_b);
      SVN_ERR(determine_merges_performed(&merges, merge_b->target, &range,
                                         depth, adm_access, notify_b, merge_b,
                                         iterpool));
      if (! merge_b->operative_merge)
        {
          if (merge_b->override_set)
            {
              /* get_mergeinfo_paths() may have made some mergeinfo
                 modifications that must be removed if this is a
                 no-op merge. */
              for (i = 0; i < children_with_mergeinfo->nelts; i++)
                {
                  svn_client__merge_path_t *child =
                    APR_ARRAY_IDX(children_with_mergeinfo,
                                  i, svn_client__merge_path_t *);
                  if (child)
                    SVN_ERR(svn_wc_prop_set2(SVN_PROP_MERGEINFO,
                                             child->propval, child->path,
                                             adm_access, TRUE, iterpool));
                }
            }
          svn_pool_destroy(iterpool);
          return err;
        }
      SVN_ERR(record_mergeinfo_on_merged_children(depth, adm_access, notify_b,
                                                  merge_b, iterpool));
      SVN_ERR(update_wc_mergeinfo(merge_b->target, parent_entry,
                                  mergeinfo_path, merges,
                                  is_rollback, adm_access, merge_b->ctx,
                                  iterpool));
      for (i = 0; i < children_with_mergeinfo->nelts; i++)
        {
          const char *child_repos_path;
          const char *child_merge_src_canon_path;
          const svn_wc_entry_t *child_entry;
          svn_client__merge_path_t *child =
                         APR_ARRAY_IDX(children_with_mergeinfo, i,
                                       svn_client__merge_path_t *);
          if (!child || child->absent)
            continue;

          if (strlen(child->path) == merge_target_len)
            child_repos_path = "";
          else
            child_repos_path = child->path +
              (merge_target_len ? merge_target_len + 1 : 0);
          child_merge_src_canon_path = svn_path_join(mergeinfo_path,
                                                     child_repos_path,
                                                     iterpool);
          SVN_ERR(svn_wc__entry_versioned(&child_entry, child->path,
                                          adm_access, FALSE, iterpool));

          if (merge_b->operative_merge)
            {
              apr_array_header_t *child_merge_rangelist;
              svn_merge_range_t *child_merge_range;
              apr_hash_t *child_merges = apr_hash_make(iterpool);
              child_merge_range = svn_merge_range_dup(&range, iterpool);
              if (child_entry->kind == svn_node_file)
                child_merge_range->inheritable = TRUE;
              else
                child_merge_range->inheritable =
                                  (!(child->missing_child)
                                     && (depth == svn_depth_infinity
                                         || depth == svn_depth_immediates));
              child_merge_rangelist =
                                 apr_array_make(iterpool, 1,
                                                sizeof(child_merge_range));
              APR_ARRAY_PUSH(child_merge_rangelist,
                             svn_merge_range_t *) = child_merge_range;
              apr_hash_set(child_merges, child->path, APR_HASH_KEY_STRING,
                           child_merge_rangelist);
              /* If merge target has indirect mergeinfo set it before
                 recording the first merge range. */
              if (child->indirect_mergeinfo)
                {
                  SVN_ERR(svn_client__record_wc_mergeinfo(
                                                   child->path,
                                                   child->pre_merge_mergeinfo,
                                                   adm_access,
                                                   iterpool));
                }
              SVN_ERR(update_wc_mergeinfo(child->path, child_entry,
                                          child_merge_src_canon_path,
                                          child_merges, is_rollback,
                                          adm_access, merge_b->ctx, iterpool));
            }
          SVN_ERR(mark_mergeinfo_as_inheritable_for_a_range(
                                                   child->pre_merge_mergeinfo,
                                                   TRUE,
                                                   &range,
                                                   child_merge_src_canon_path,
                                                   child->path,
                                                   adm_access,
                                                   merge_b,
                                                   children_with_mergeinfo,
                                                   i, iterpool));
          if (i > 0)
            SVN_ERR(svn_client__elide_mergeinfo(child->path, merge_b->target,
                                                child_entry, adm_access,
                                                merge_b->ctx, iterpool));
        } /* (i = 0; i < children_with_mergeinfo->nelts; i++) */
    } /* (!merge_b->dry_run && merge_b->same_repos) */

  svn_pool_destroy(iterpool);
  return err;
}


/* Drive a merge of MERGE_SOURCES into working copy path TARGET (with
   associated TARGET_ENTRY and ADM_ACCESS baton).  

   If SOURCES_ANCESTRAL is set, then for every merge source in
   MERGE_SOURCES, the "left" and "right" side of the merge source are
   ancestrally related.  (See 'MERGEINFO MERGE SOURCE NORMALIZATION'
   for more on what that means and how it matters.)  

   If SOURCES_RELATED is set, the "left" and "right" sides of the
   merge source are historically related (ancestors, uncles, second
   cousins thrice removed, etc...).  (This is passed through to
   do_file_merge() to simulate the history checks that the repository
   logic does in the directory case.)

   SAME_REPOS is TRUE iff the merge sources live in the same
   repository as the one from which the target working copy has been
   checked out.

   FORCE, DRY_RUN, RECORD_ONLY, IGNORE_ANCESTRY, DEPTH, MERGE_OPTIONS,
   and CTX are as described in the docstring for svn_client_merge_peg3().
*/
static svn_error_t *
do_merge(apr_array_header_t *merge_sources,
         const char *target,
         const svn_wc_entry_t *target_entry,
         svn_wc_adm_access_t *adm_access,
         svn_boolean_t sources_ancestral,
         svn_boolean_t sources_related,
         svn_boolean_t same_repos,
         svn_boolean_t ignore_ancestry,
         svn_boolean_t force,
         svn_boolean_t dry_run,
         svn_boolean_t record_only,
         svn_depth_t depth,
         const apr_array_header_t *merge_options,
         svn_client_ctx_t *ctx,
         apr_pool_t *pool)
{
  apr_pool_t *subpool = svn_pool_create(pool);
  merge_cmd_baton_t merge_cmd_baton;
  notification_receiver_baton_t notify_baton;
  svn_config_t *cfg;
  const char *diff3_cmd;
  int i;
  svn_boolean_t checked_mergeinfo_capability = FALSE;

  /* If this is a dry-run record-only merge, there's nothing to do. */
  if (record_only && dry_run)
    return SVN_NO_ERROR;

  /* Sanity check: we can do a record-only merge (which is a
     merge-tracking thing) if the sources aren't related, because we
     don't do merge-tracking if the sources aren't related.  */
  if (record_only && (! sources_ancestral))
    return svn_error_create(SVN_ERR_INCORRECT_PARAMS, NULL,
                            _("Use of two URLs is not compatible with "
                              "mergeinfo modification"));

  /* Ensure a known depth. */
  if (depth == svn_depth_unknown)
    depth = target_entry->depth;

  /* Set up the diff3 command, so various callers don't have to. */
  cfg = ctx->config ? apr_hash_get(ctx->config, SVN_CONFIG_CATEGORY_CONFIG,
                                   APR_HASH_KEY_STRING) : NULL;
  svn_config_get(cfg, &diff3_cmd, SVN_CONFIG_SECTION_HELPERS,
                 SVN_CONFIG_OPTION_DIFF3_CMD, NULL);


  /* Build the merge context baton (or at least the parts of it that
     don't need to be reset for each merge source).  */
  merge_cmd_baton.force = force;
  merge_cmd_baton.dry_run = dry_run;
  merge_cmd_baton.record_only = record_only;
  merge_cmd_baton.ignore_ancestry = ignore_ancestry;
  merge_cmd_baton.same_repos = same_repos;
  merge_cmd_baton.mergeinfo_capable = FALSE;
  merge_cmd_baton.sources_ancestral = sources_ancestral;
  merge_cmd_baton.ctx = ctx;
  merge_cmd_baton.target_missing_child = FALSE;
  merge_cmd_baton.target = target;
  merge_cmd_baton.pool = subpool;
  merge_cmd_baton.merge_options = merge_options;
  merge_cmd_baton.diff3_cmd = diff3_cmd;

  /* Build the notification receiver baton. */
  notify_baton.wrapped_func = ctx->notify_func2;
  notify_baton.wrapped_baton = ctx->notify_baton2;
  notify_baton.nbr_notifications = 0;
  notify_baton.nbr_operative_notifications = 0;
  notify_baton.merged_paths = NULL;
  notify_baton.skipped_paths = NULL;
  notify_baton.is_single_file_merge = FALSE;
  notify_baton.children_with_mergeinfo = NULL;
  notify_baton.cur_ancestor_index = -1;
  notify_baton.merge_b = &merge_cmd_baton;
  notify_baton.pool = pool;

  for (i = 0; i < merge_sources->nelts; i++)
    {
      merge_source_t *merge_source = 
        APR_ARRAY_IDX(merge_sources, i, merge_source_t *);
      const char *url1, *url2;
      svn_revnum_t rev1, rev2;
      svn_ra_session_t *ra_session1, *ra_session2;

      svn_pool_clear(subpool);

      /* Convenience variables. */
      url1 = merge_source->url1;
      url2 = merge_source->url2;
      rev1 = merge_source->rev1;
      rev2 = merge_source->rev2;

      /* Sanity check:  if our left- and right-side merge sources are
         the same, there's nothing to here. */
      if ((strcmp(url1, url2) == 0) && (rev1 == rev2))
        continue;

      /* Establish RA sessions to our URLs. */
      SVN_ERR(svn_client__open_ra_session_internal(&ra_session1, url1,
                                                   NULL, NULL, NULL, 
                                                   FALSE, TRUE, ctx, subpool));
      SVN_ERR(svn_client__open_ra_session_internal(&ra_session2, url2,
                                                   NULL, NULL, NULL, 
                                                   FALSE, TRUE, ctx, subpool));

      /* Populate the portions of the merge context baton that need to
         be reset for each merge source iteration. */
      merge_cmd_baton.url = url2;
      merge_cmd_baton.added_path = NULL;
      merge_cmd_baton.add_necessitated_merge = FALSE;
      merge_cmd_baton.dry_run_deletions = 
        dry_run ? apr_hash_make(subpool) : NULL;
      merge_cmd_baton.conflicted_paths = NULL;
      merge_cmd_baton.operative_merge = FALSE;
      merge_cmd_baton.target_has_dummy_merge_range = FALSE;
      merge_cmd_baton.override_set = FALSE;
      merge_cmd_baton.ra_session1 = ra_session1;
      merge_cmd_baton.ra_session2 = ra_session2;

      /* Populate the portions of the merge context baton that require
         an RA session to set, but shouldn't be reset for each iteration. */
      if (! checked_mergeinfo_capability)
        {
          SVN_ERR(svn_ra_has_capability(ra_session1,
                                        &merge_cmd_baton.mergeinfo_capable,
                                        SVN_RA_CAPABILITY_MERGEINFO, subpool));
          checked_mergeinfo_capability = TRUE;
        }

      /* If this is a record-only merge and our sources are from the
         same repository as our target, just do the record and move on. */
      if (same_repos && record_only)
        {
          const char *merge_source_url = (rev1 < rev2) ? url2 : url1;
          svn_merge_range_t range;
          range.start = rev1;
          range.end = rev2;
          range.inheritable = TRUE;
          SVN_ERR(record_mergeinfo_for_record_only_merge(merge_source_url,
                                                         &range,
                                                         target_entry, 
                                                         adm_access,
                                                         &merge_cmd_baton,
                                                         subpool));

          continue;
        }

      /* Call our merge helpers based on entry kind. */
      if (target_entry->kind == svn_node_file)
        {
          SVN_ERR(do_file_merge(url1, rev1, url2, rev2, target, 
                                sources_related, adm_access, 
                                &notify_baton, &merge_cmd_baton, subpool));
        }
      else if (target_entry->kind == svn_node_dir)
        {
          SVN_ERR(do_directory_merge(url1, rev1, url2, rev2, target_entry, 
                                     adm_access, depth, &notify_baton,
                                     &merge_cmd_baton, subpool));
        }

      /* The final mergeinfo on TARGET_WCPATH may itself elide. */
      if ((! dry_run) && merge_cmd_baton.operative_merge)
        SVN_ERR(svn_client__elide_mergeinfo(target, NULL, target_entry,
                                            adm_access, ctx, subpool));
    }

  svn_pool_destroy(subpool);
  return SVN_NO_ERROR;
}


/*-----------------------------------------------------------------------*/
\f
/*** Public APIs ***/

svn_error_t *
svn_client_merge3(const char *source1,
                  const svn_opt_revision_t *revision1,
                  const char *source2,
                  const svn_opt_revision_t *revision2,
                  const char *target_wcpath,
                  svn_depth_t depth,
                  svn_boolean_t ignore_ancestry,
                  svn_boolean_t force,
                  svn_boolean_t record_only,
                  svn_boolean_t dry_run,
                  const apr_array_header_t *merge_options,
                  svn_client_ctx_t *ctx,
                  apr_pool_t *pool)
{
  svn_wc_adm_access_t *adm_access;
  const svn_wc_entry_t *entry;
  const char *URL1, *URL2;
  svn_revnum_t rev1, rev2;
  svn_boolean_t related = FALSE, ancestral = FALSE;
  const char *wc_repos_root, *source_repos_root;
  svn_revnum_t youngest_rev = SVN_INVALID_REVNUM;
  svn_ra_session_t *ra_session1, *ra_session2;
  apr_array_header_t *merge_sources;
  merge_source_t *merge_source;
  svn_opt_revision_t working_rev;
  const char *yc_path = NULL;
  svn_revnum_t yc_rev = SVN_INVALID_REVNUM;
  apr_pool_t *sesspool;
  svn_boolean_t same_repos;

  /* Sanity check our input -- we require specified revisions. */
  if ((revision1->kind == svn_opt_revision_unspecified)
      || (revision2->kind == svn_opt_revision_unspecified))
    return svn_error_create(SVN_ERR_CLIENT_BAD_REVISION, NULL,
                            _("Not all required revisions are specified"));

  /* ### FIXME: This function really ought to do a history check on
     the left and right sides of the merge source, and -- if one is an
     ancestor of the other -- just call svn_client_merge_peg3() with
     the appropriate args. */

  /* If source1 or source2 are paths, we need to get the underlying
     URL from the wc and save the initial path we were passed so we
     can use it as a path parameter (either in the baton or not).
     otherwise, the path will just be NULL, which means we won't be
     able to figure out some kind of revision specifications, but in
     that case it won't matter, because those ways of specifying a
     revision are meaningless for a url. */
  SVN_ERR(svn_client_url_from_path(&URL1, source1, pool));
  if (! URL1)
    return svn_error_createf(SVN_ERR_ENTRY_MISSING_URL, NULL,
                             _("'%s' has no URL"),
                             svn_path_local_style(source1, pool));

  SVN_ERR(svn_client_url_from_path(&URL2, source2, pool));
  if (! URL2)
    return svn_error_createf(SVN_ERR_ENTRY_MISSING_URL, NULL,
                             _("'%s' has no URL"),
                             svn_path_local_style(source2, pool));

  /* Open an admistrative session with the working copy. */
  SVN_ERR(svn_wc_adm_probe_open3(&adm_access, NULL, target_wcpath,
                                 ! dry_run, -1, ctx->cancel_func,
                                 ctx->cancel_baton, pool));

  /* Fetch the target's entry. */
  SVN_ERR(svn_wc__entry_versioned(&entry, target_wcpath, adm_access, 
                                  FALSE, pool));

  /* Determine the working copy target's repository root URL. */
  working_rev.kind = svn_opt_revision_working;
  SVN_ERR(svn_client__get_repos_root(&wc_repos_root, target_wcpath,
                                     &working_rev, adm_access, ctx, pool));

  /* Open some RA sessions to our merge source sides. */
  sesspool = svn_pool_create(pool);
  SVN_ERR(svn_client__open_ra_session_internal(&ra_session1,
                                               URL1, NULL, NULL, NULL,
                                               FALSE, TRUE, ctx, sesspool));
  SVN_ERR(svn_client__open_ra_session_internal(&ra_session2,
                                               URL2, NULL, NULL, NULL,
                                               FALSE, TRUE, ctx, sesspool));

  /* Resolve revisions to real numbers. */
  SVN_ERR(svn_client__get_revision_number(&rev1, &youngest_rev, ra_session1, 
                                          revision1, NULL, sesspool));
  SVN_ERR(svn_client__get_revision_number(&rev2, &youngest_rev, ra_session2, 
                                          revision2, NULL, sesspool));

  /* Get the repository root URL from one of our sessions (the other
     doesn't matter -- if it ain't the same, other stuff would fall
     over later).  We have to dup this into our pool, since the API
     declares that this data will live in the session's pool.  */
  SVN_ERR(svn_ra_get_repos_root(ra_session1, &source_repos_root, sesspool));
  source_repos_root = apr_pstrdup(pool, source_repos_root);

  /* Do our working copy and sources come from the same repository? */
  same_repos = (strcmp(source_repos_root, wc_repos_root) == 0) ? TRUE : FALSE;

  /* Unless we're ignoring ancestry, see if the two sources are related.  */
  if (! ignore_ancestry)
    {
      svn_opt_revision_t opt_rev1, opt_rev2;
      opt_rev1.kind = opt_rev2.kind = svn_opt_revision_number;
      opt_rev1.value.number = rev1;
      opt_rev2.value.number = rev2;
      SVN_ERR(svn_client__get_youngest_common_ancestor(&yc_path, &yc_rev,
                                                       URL1, &opt_rev1,
                                                       URL2, &opt_rev2,
                                                       ctx, pool));
    }

  /* Check for a youngest common ancestor.  If we have one, we'll be
     doing merge tracking.

     So, given a requested merge of the differences between A and
     B, and a common ancestor of C, we will find ourselves in one of
     four positions, and four different approaches:
 
        A == B == C   there's nothing to merge

        A == C != B   we merge the changes between A (or C) and B

        B == C != A   we merge the changes between B (or C) and A

        A != B != C   we merge the changes between A and B without
                      merge recording, then record-only two merges:
                      from A to C, and from C to B
  */
  if (yc_path && SVN_IS_VALID_REVNUM(yc_rev))
    {
      apr_array_header_t *ranges;
      svn_opt_revision_range_t *range;
      svn_opt_revision_t peg_revision;
      peg_revision.kind = svn_opt_revision_number;

      /* Note that our merge sources are related. */
      related = TRUE;
      
      /* Make YC_PATH into a full URL. */
      yc_path = svn_path_join(source_repos_root, 
                              svn_path_uri_encode(yc_path, pool), pool);

      /* If the common ancestor matches the right side of our merge,
         then we only need to reverse-merge the left side. */
      if ((strcmp(yc_path, URL2) == 0) && (yc_rev == rev2))
        {
          ancestral = TRUE;
          range = apr_pcalloc(pool, sizeof(*range));
          range->start.kind = svn_opt_revision_number;
          range->start.value.number = rev1;
          range->end.kind = svn_opt_revision_number;
          range->end.value.number = yc_rev;
          ranges = apr_array_make(pool, 2, sizeof(svn_opt_revision_range_t *));
          APR_ARRAY_PUSH(ranges, svn_opt_revision_range_t *) = range;
          peg_revision.value.number = rev1;
          SVN_ERR(normalize_merge_sources(&merge_sources, URL1, URL1,
                                          source_repos_root, &peg_revision, 
                                          ranges, ra_session1, ctx, pool));
        }
      /* If the common ancestor matches the left side of our merge,
         then we only need to merge the right side. */
      else if ((strcmp(yc_path, URL1) == 0) && (yc_rev == rev1))
        {
          ancestral = TRUE;
          range = apr_pcalloc(pool, sizeof(*range));
          range->start.kind = svn_opt_revision_number;
          range->start.value.number = yc_rev;
          range->end.kind = svn_opt_revision_number;
          range->end.value.number = rev2;
          ranges = apr_array_make(pool, 2, sizeof(svn_opt_revision_range_t *));
          APR_ARRAY_PUSH(ranges, svn_opt_revision_range_t *) = range;
          peg_revision.value.number = rev2;
          SVN_ERR(normalize_merge_sources(&merge_sources, URL2, URL2,
                                          source_repos_root, &peg_revision, 
                                          ranges, ra_session2, ctx, pool));
        }
      /* And otherwise, we need to do both: reverse merge the left
         side, and merge the right. */
      else
        {
          apr_array_header_t *remove_sources, *add_sources;

          range = apr_pcalloc(pool, sizeof(*range));
          range->start.kind = svn_opt_revision_number;
          range->start.value.number = rev1;
          range->end.kind = svn_opt_revision_number;
          range->end.value.number = yc_rev;
          ranges = apr_array_make(pool, 2, sizeof(svn_opt_revision_range_t *));
          APR_ARRAY_PUSH(ranges, svn_opt_revision_range_t *) = range;
          peg_revision.value.number = rev1;
          SVN_ERR(normalize_merge_sources(&remove_sources, URL1, URL1,
                                          source_repos_root, &peg_revision, 
                                          ranges, ra_session1, ctx, pool));

          range = apr_pcalloc(pool, sizeof(*range));
          range->start.kind = svn_opt_revision_number;
          range->start.value.number = yc_rev;
          range->end.kind = svn_opt_revision_number;
          range->end.value.number = rev2;
          ranges = apr_array_make(pool, 2, sizeof(svn_opt_revision_range_t *));
          APR_ARRAY_PUSH(ranges, svn_opt_revision_range_t *) = range;
          peg_revision.value.number = rev2;
          SVN_ERR(normalize_merge_sources(&add_sources, URL2, URL2,
                                          source_repos_root, &peg_revision, 
                                          ranges, ra_session2, ctx, pool));

          /* Close our temporary RA sessions. */
          svn_pool_destroy(sesspool);

          /* If this isn't a record-only merge, we'll first do a stupid
             point-to-point merge... */
          if (! record_only)
            {
              merge_source_t *faux_source;
              apr_array_header_t *faux_sources = 
                apr_array_make(pool, 1, sizeof(merge_source_t *));
              faux_source = apr_pcalloc(pool, sizeof(*faux_source));
              faux_source->url1 = URL1;
              faux_source->url2 = URL2;
              faux_source->rev1 = rev1;
              faux_source->rev2 = rev2;
              APR_ARRAY_PUSH(faux_sources, merge_source_t *) = faux_source;
              SVN_ERR(do_merge(faux_sources, target_wcpath, entry, adm_access, 
                               ancestral, related, same_repos,
                               ignore_ancestry, force, dry_run, 
                               record_only, depth, merge_options, ctx, pool));
            }
          /* ... and now we do a pair of record-only merges using the real
             sources we've calculated.  (We know that each tong in our
             fork of our merge source history tree has an ancestral
             relationship with the common ancestral, so we force
             ancestral=TRUE here.) */
          SVN_ERR(do_merge(add_sources, target_wcpath, entry, adm_access, 
                           TRUE, related, same_repos,
                           ignore_ancestry, force, dry_run, 
                           TRUE, depth, merge_options, ctx, pool));
          SVN_ERR(do_merge(remove_sources, target_wcpath, entry, adm_access, 
                           TRUE, related, same_repos,
                           ignore_ancestry, force, dry_run, 
                           TRUE, depth, merge_options, ctx, pool));

          SVN_ERR(svn_wc_adm_close(adm_access));
          return SVN_NO_ERROR;
        }
    }
  else
    {
      /* Build a single-item merge_source_t array. */
      merge_sources = apr_array_make(pool, 1, sizeof(merge_source_t *));
      merge_source = apr_pcalloc(pool, sizeof(*merge_source));
      merge_source->url1 = URL1;
      merge_source->url2 = URL2;
      merge_source->rev1 = rev1;
      merge_source->rev2 = rev2;
      APR_ARRAY_PUSH(merge_sources, merge_source_t *) = merge_source;
    }

  /* Close our temporary RA sessions. */
  svn_pool_destroy(sesspool);

  SVN_ERR(do_merge(merge_sources, target_wcpath, entry, adm_access, 
                   ancestral, related, same_repos,
                   ignore_ancestry, force, dry_run, 
                   record_only, depth, merge_options, ctx, pool));

  SVN_ERR(svn_wc_adm_close(adm_access));

  return SVN_NO_ERROR;
}

svn_error_t *
svn_client_merge2(const char *source1,
                  const svn_opt_revision_t *revision1,
                  const char *source2,
                  const svn_opt_revision_t *revision2,
                  const char *target_wcpath,
                  svn_boolean_t recurse,
                  svn_boolean_t ignore_ancestry,
                  svn_boolean_t force,
                  svn_boolean_t dry_run,
                  const apr_array_header_t *merge_options,
                  svn_client_ctx_t *ctx,
                  apr_pool_t *pool)
{
  return svn_client_merge3(source1, revision1, source2, revision2,
                           target_wcpath,
                           SVN_DEPTH_INFINITY_OR_FILES(recurse),
                           ignore_ancestry, force, FALSE, dry_run,
                           merge_options, ctx, pool);
}

svn_error_t *
svn_client_merge(const char *source1,
                 const svn_opt_revision_t *revision1,
                 const char *source2,
                 const svn_opt_revision_t *revision2,
                 const char *target_wcpath,
                 svn_boolean_t recurse,
                 svn_boolean_t ignore_ancestry,
                 svn_boolean_t force,
                 svn_boolean_t dry_run,
                 svn_client_ctx_t *ctx,
                 apr_pool_t *pool)
{
  return svn_client_merge2(source1, revision1, source2, revision2,
                           target_wcpath, recurse, ignore_ancestry, force,
                           dry_run, NULL, ctx, pool);
}


svn_error_t *
svn_client_merge_peg3(const char *source,
                      const apr_array_header_t *ranges_to_merge,
                      const svn_opt_revision_t *peg_revision,
                      const char *target_wcpath,
                      svn_depth_t depth,
                      svn_boolean_t ignore_ancestry,
                      svn_boolean_t force,
                      svn_boolean_t record_only,
                      svn_boolean_t dry_run,
                      const apr_array_header_t *merge_options,
                      svn_client_ctx_t *ctx,
                      apr_pool_t *pool)
{
  svn_wc_adm_access_t *adm_access;
  const svn_wc_entry_t *entry;
  const char *URL;
  apr_array_header_t *merge_sources;
  const char *wc_repos_root, *source_repos_root;
  svn_opt_revision_t working_rev;
  svn_ra_session_t *ra_session;
  apr_pool_t *sesspool;

  /* No ranges to merge?  No problem. */
  if (ranges_to_merge->nelts == 0)
    return SVN_NO_ERROR;

  /* Open an admistrative session with the working copy. */
  SVN_ERR(svn_wc_adm_probe_open3(&adm_access, NULL, target_wcpath,
                                 (! dry_run), -1, ctx->cancel_func,
                                 ctx->cancel_baton, pool));

  /* Fetch the target's entry. */
  SVN_ERR(svn_wc__entry_versioned(&entry, target_wcpath, adm_access, 
                                  FALSE, pool));

  /* Make sure we're dealing with a real URL. */
  SVN_ERR(svn_client_url_from_path(&URL, source, pool));
  if (! URL)
    return svn_error_createf(SVN_ERR_ENTRY_MISSING_URL, NULL,
                             _("'%s' has no URL"),
                             svn_path_local_style(source, pool));

  /* Determine the working copy target's repository root URL. */
  working_rev.kind = svn_opt_revision_working;
  SVN_ERR(svn_client__get_repos_root(&wc_repos_root, target_wcpath,
                                     &working_rev, adm_access, ctx, pool));

  /* Open an RA session to our source URL, and determine its root URL. */
  sesspool = svn_pool_create(pool);
  SVN_ERR(svn_client__open_ra_session_internal(&ra_session,
                                               URL, NULL, NULL, NULL,
                                               FALSE, TRUE, ctx, sesspool));
  SVN_ERR(svn_ra_get_repos_root(ra_session, &source_repos_root, pool));

  /* Normalize our merge sources. */
  SVN_ERR(normalize_merge_sources(&merge_sources, source, URL, 
                                  source_repos_root, peg_revision, 
                                  ranges_to_merge, ra_session, ctx, pool));

  /* We're done with our little RA session. */
  svn_pool_destroy(sesspool);

  /* Do the real merge!  (We say with confidence that our merge
     sources are both ancestral and related.) */
  SVN_ERR(do_merge(merge_sources, target_wcpath, entry, adm_access,
                   TRUE, TRUE,
                   (strcmp(wc_repos_root, source_repos_root) == 0),
                   ignore_ancestry, force, dry_run, record_only, depth,
                   merge_options, ctx, pool));

  /* Shutdown the administrative session. */
  SVN_ERR(svn_wc_adm_close(adm_access));

  return SVN_NO_ERROR;
}


svn_error_t *
svn_client_merge_peg2(const char *source,
                      const svn_opt_revision_t *revision1,
                      const svn_opt_revision_t *revision2,
                      const svn_opt_revision_t *peg_revision,
                      const char *target_wcpath,
                      svn_boolean_t recurse,
                      svn_boolean_t ignore_ancestry,
                      svn_boolean_t force,
                      svn_boolean_t dry_run,
                      const apr_array_header_t *merge_options,
                      svn_client_ctx_t *ctx,
                      apr_pool_t *pool)
{
  svn_opt_revision_range_t range;
  apr_array_header_t *ranges_to_merge =
    apr_array_make(pool, 1, sizeof(svn_opt_revision_range_t *));

  range.start = *revision1;
  range.end = *revision2;
  APR_ARRAY_PUSH(ranges_to_merge, svn_opt_revision_range_t *) = &range;
  return svn_client_merge_peg3(source, ranges_to_merge,
                               peg_revision,
                               target_wcpath,
                               SVN_DEPTH_INFINITY_OR_FILES(recurse),
                               ignore_ancestry, force, FALSE, dry_run,
                               merge_options, ctx, pool);
}

svn_error_t *
svn_client_merge_peg(const char *source,
                     const svn_opt_revision_t *revision1,
                     const svn_opt_revision_t *revision2,
                     const svn_opt_revision_t *peg_revision,
                     const char *target_wcpath,
                     svn_boolean_t recurse,
                     svn_boolean_t ignore_ancestry,
                     svn_boolean_t force,
                     svn_boolean_t dry_run,
                     svn_client_ctx_t *ctx,
                     apr_pool_t *pool)
{
  return svn_client_merge_peg2(source, revision1, revision2, peg_revision,
                               target_wcpath, recurse, ignore_ancestry, force,
                               dry_run, NULL, ctx, pool);
}