reftable/reader: introduce refcounting

[git/gitster.git] / refs.h

#ifndef REFS_H
#define REFS_H

#include "commit.h"
#include "repository.h"

struct object_id;
struct ref_store;
struct strbuf;
struct string_list;
struct string_list_item;
struct worktree;

enum ref_storage_format ref_storage_format_by_name(const char *name);
const char *ref_storage_format_to_name(enum ref_storage_format ref_storage_format);

/*
 * Resolve a reference, recursively following symbolic refererences.
 *
 * Return the name of the non-symbolic reference that ultimately pointed
 * at the resolved object name.  The return value, if not NULL, is a
 * pointer into either a static buffer or the input ref.
 *
 * If oid is non-NULL, store the referred-to object's name in it.
 *
 * If the reference cannot be resolved to an object, the behavior
 * depends on the RESOLVE_REF_READING flag:
 *
 * - If RESOLVE_REF_READING is set, return NULL.
 *
 * - If RESOLVE_REF_READING is not set, clear oid and return the name of
 *   the last reference name in the chain, which will either be a non-symbolic
 *   reference or an undefined reference.  If this is a prelude to
 *   "writing" to the ref, the return value is the name of the ref
 *   that will actually be created or changed.
 *
 * If the RESOLVE_REF_NO_RECURSE flag is passed, only resolves one
 * level of symbolic reference.  The value stored in oid for a symbolic
 * reference will always be null_oid in this case, and the return
 * value is the reference that the symref refers to directly.
 *
 * If flags is non-NULL, set the value that it points to the
 * combination of REF_ISPACKED (if the reference was found among the
 * packed references), REF_ISSYMREF (if the initial reference was a
 * symbolic reference), REF_BAD_NAME (if the reference name is ill
 * formed --- see RESOLVE_REF_ALLOW_BAD_NAME below), and REF_ISBROKEN
 * (if the ref is malformed or has a bad name). See refs.h for more detail
 * on each flag.
 *
 * If ref is not a properly-formatted, normalized reference, return
 * NULL.  If more than MAXDEPTH recursive symbolic lookups are needed,
 * give up and return NULL.
 *
 * RESOLVE_REF_ALLOW_BAD_NAME allows resolving refs even when their
 * name is invalid according to git-check-ref-format(1).  If the name
 * is bad then the value stored in oid will be null_oid and the two
 * flags REF_ISBROKEN and REF_BAD_NAME will be set.
 *
 * Even with RESOLVE_REF_ALLOW_BAD_NAME, names that escape the refs/
 * directory and do not consist of all caps and underscores cannot be
 * resolved. The function returns NULL for such ref names.
 * Caps and underscores refers to the pseudorefs, such as HEAD,
 * FETCH_HEAD and friends, that all live outside of the refs/ directory.
 */
#define RESOLVE_REF_READING 0x01
#define RESOLVE_REF_NO_RECURSE 0x02
#define RESOLVE_REF_ALLOW_BAD_NAME 0x04

const char *refs_resolve_ref_unsafe(struct ref_store *refs,
                                    const char *refname,
                                    int resolve_flags,
                                    struct object_id *oid,
                                    int *flags);

char *refs_resolve_refdup(struct ref_store *refs,
                          const char *refname, int resolve_flags,
                          struct object_id *oid, int *flags);

int refs_read_ref_full(struct ref_store *refs, const char *refname,
                       int resolve_flags, struct object_id *oid, int *flags);

int refs_read_ref(struct ref_store *refs, const char *refname, struct object_id *oid);

int refs_read_symbolic_ref(struct ref_store *ref_store, const char *refname,
                           struct strbuf *referent);

/*
 * Return 0 if a reference named refname could be created without
 * conflicting with the name of an existing reference. Otherwise,
 * return a negative value and write an explanation to err. If extras
 * is non-NULL, it is a list of additional refnames with which refname
 * is not allowed to conflict. If skip is non-NULL, ignore potential
 * conflicts with refs in skip (e.g., because they are scheduled for
 * deletion in the same operation). Behavior is undefined if the same
 * name is listed in both extras and skip.
 *
 * Two reference names conflict if one of them exactly matches the
 * leading components of the other; e.g., "foo/bar" conflicts with
 * both "foo" and with "foo/bar/baz" but not with "foo/bar" or
 * "foo/barbados".
 *
 * extras and skip must be sorted.
 */

int refs_verify_refname_available(struct ref_store *refs,
                                  const char *refname,
                                  const struct string_list *extras,
                                  const struct string_list *skip,
                                  struct strbuf *err);

int refs_ref_exists(struct ref_store *refs, const char *refname);

int should_autocreate_reflog(const char *refname);

int is_branch(const char *refname);

#define REF_STORE_CREATE_ON_DISK_IS_WORKTREE (1 << 0)

int ref_store_create_on_disk(struct ref_store *refs, int flags, struct strbuf *err);

/*
 * Release all memory and resources associated with the ref store.
 */
void ref_store_release(struct ref_store *ref_store);

/*
 * Remove the ref store from disk. This deletes all associated data.
 */
int ref_store_remove_on_disk(struct ref_store *refs, struct strbuf *err);

/*
 * Return the peeled value of the oid currently being iterated via
 * for_each_ref(), etc. This is equivalent to calling:
 *
 *   peel_object(r, oid, &peeled);
 *
 * with the "oid" value given to the each_ref_fn callback, except
 * that some ref storage may be able to answer the query without
 * actually loading the object in memory.
 */
int peel_iterated_oid(struct repository *r,
                      const struct object_id *base, struct object_id *peeled);

/**
 * Resolve refname in the nested "gitlink" repository in the specified
 * submodule (which must be non-NULL). If the resolution is
 * successful, return 0 and set oid to the name of the object;
 * otherwise, return a non-zero value.
 */
int repo_resolve_gitlink_ref(struct repository *r,
                             const char *submodule, const char *refname,
                             struct object_id *oid);

/*
 * Return true iff abbrev_name is a possible abbreviation for
 * full_name according to the rules defined by ref_rev_parse_rules in
 * refs.c.
 */
int refname_match(const char *abbrev_name, const char *full_name);

/*
 * Given a 'prefix' expand it by the rules in 'ref_rev_parse_rules' and add
 * the results to 'prefixes'
 */
struct strvec;
void expand_ref_prefix(struct strvec *prefixes, const char *prefix);

int expand_ref(struct repository *r, const char *str, int len, struct object_id *oid, char **ref);
int repo_dwim_ref(struct repository *r, const char *str, int len,
                  struct object_id *oid, char **ref, int nonfatal_dangling_mark);
int repo_dwim_log(struct repository *r, const char *str, int len, struct object_id *oid, char **ref);

/*
 * Retrieves the default branch name for newly-initialized repositories.
 *
 * The return value is an allocated string.
 */
char *repo_default_branch_name(struct repository *r, int quiet);

/*
 * A ref_transaction represents a collection of reference updates that
 * should succeed or fail together.
 *
 * Calling sequence
 * ----------------
 *
 * - Allocate and initialize a `struct ref_transaction` by calling
 *   `ref_transaction_begin()`.
 *
 * - Specify the intended ref updates by calling one or more of the
 *   following functions:
 *   - `ref_transaction_update()`
 *   - `ref_transaction_create()`
 *   - `ref_transaction_delete()`
 *   - `ref_transaction_verify()`
 *
 * - Then either:
 *
 *   - Optionally call `ref_transaction_prepare()` to prepare the
 *     transaction. This locks all references, checks preconditions,
 *     etc. but doesn't finalize anything. If this step fails, the
 *     transaction has been closed and can only be freed. If this step
 *     succeeds, then `ref_transaction_commit()` is almost certain to
 *     succeed. However, you can still call `ref_transaction_abort()`
 *     if you decide not to commit the transaction after all.
 *
 *   - Call `ref_transaction_commit()` to execute the transaction,
 *     make the changes permanent, and release all locks. If you
 *     haven't already called `ref_transaction_prepare()`, then
 *     `ref_transaction_commit()` calls it for you.
 *
 *   Or
 *
 *   - Call `initial_ref_transaction_commit()` if the ref database is
 *     known to be empty and have no other writers (e.g. during
 *     clone). This is likely to be much faster than
 *     `ref_transaction_commit()`. `ref_transaction_prepare()` should
 *     *not* be called before `initial_ref_transaction_commit()`.
 *
 * - Then finally, call `ref_transaction_free()` to free the
 *   `ref_transaction` data structure.
 *
 * At any time before calling `ref_transaction_commit()`, you can call
 * `ref_transaction_abort()` to abort the transaction, rollback any
 * locks, and free any associated resources (including the
 * `ref_transaction` data structure).
 *
 * Putting it all together, a complete reference update looks like
 *
 *         struct ref_transaction *transaction;
 *         struct strbuf err = STRBUF_INIT;
 *         int ret = 0;
 *
 *         transaction = ref_store_transaction_begin(refs, &err);
 *         if (!transaction ||
 *             ref_transaction_update(...) ||
 *             ref_transaction_create(...) ||
 *             ...etc... ||
 *             ref_transaction_commit(transaction, &err)) {
 *                 error("%s", err.buf);
 *                 ret = -1;
 *         }
 *         ref_transaction_free(transaction);
 *         strbuf_release(&err);
 *         return ret;
 *
 * Error handling
 * --------------
 *
 * On error, transaction functions append a message about what
 * went wrong to the 'err' argument.  The message mentions what
 * ref was being updated (if any) when the error occurred so it
 * can be passed to 'die' or 'error' as-is.
 *
 * The message is appended to err without first clearing err.
 * err will not be '\n' terminated.
 *
 * Caveats
 * -------
 *
 * Note that no locks are taken, and no refs are read, until
 * `ref_transaction_prepare()` or `ref_transaction_commit()` is
 * called. So, for example, `ref_transaction_verify()` won't report a
 * verification failure until the commit is attempted.
 */
struct ref_transaction;

/*
 * Bit values set in the flags argument passed to each_ref_fn() and
 * stored in ref_iterator::flags. Other bits are for internal use
 * only:
 */

/* Reference is a symbolic reference. */
#define REF_ISSYMREF 0x01

/* Reference is a packed reference. */
#define REF_ISPACKED 0x02

/*
 * Reference cannot be resolved to an object name: dangling symbolic
 * reference (directly or indirectly), corrupt reference file,
 * reference exists but name is bad, or symbolic reference refers to
 * ill-formatted reference name.
 */
#define REF_ISBROKEN 0x04

/*
 * Reference name is not well formed.
 *
 * See git-check-ref-format(1) for the definition of well formed ref names.
 */
#define REF_BAD_NAME 0x08

/*
 * The signature for the callback function for the for_each_*()
 * functions below.  The memory pointed to by the refname and oid
 * arguments is only guaranteed to be valid for the duration of a
 * single callback invocation.
 */
typedef int each_ref_fn(const char *refname,
                        const struct object_id *oid, int flags, void *cb_data);

/*
 * The following functions invoke the specified callback function for
 * each reference indicated.  If the function ever returns a nonzero
 * value, stop the iteration and return that value.  Please note that
 * it is not safe to modify references while an iteration is in
 * progress, unless the same callback function invocation that
 * modifies the reference also returns a nonzero value to immediately
 * stop the iteration. Returned references are sorted.
 */
int refs_head_ref(struct ref_store *refs,
                  each_ref_fn fn, void *cb_data);
int refs_for_each_ref(struct ref_store *refs,
                      each_ref_fn fn, void *cb_data);
int refs_for_each_ref_in(struct ref_store *refs, const char *prefix,
                         each_ref_fn fn, void *cb_data);
int refs_for_each_tag_ref(struct ref_store *refs,
                          each_ref_fn fn, void *cb_data);
int refs_for_each_branch_ref(struct ref_store *refs,
                             each_ref_fn fn, void *cb_data);
int refs_for_each_remote_ref(struct ref_store *refs,
                             each_ref_fn fn, void *cb_data);
int refs_for_each_replace_ref(struct ref_store *refs,
                              each_ref_fn fn, void *cb_data);

/*
 * references matching any pattern in "exclude_patterns" are omitted from the
 * result set on a best-effort basis.
 */
int refs_for_each_fullref_in(struct ref_store *refs, const char *prefix,
                             const char **exclude_patterns,
                             each_ref_fn fn, void *cb_data);

/**
 * iterate all refs in "patterns" by partitioning patterns into disjoint sets
 * and iterating the longest-common prefix of each set.
 *
 * references matching any pattern in "exclude_patterns" are omitted from the
 * result set on a best-effort basis.
 *
 * callers should be prepared to ignore references that they did not ask for.
 */
int refs_for_each_fullref_in_prefixes(struct ref_store *refs,
                                      const char *namespace,
                                      const char **patterns,
                                      const char **exclude_patterns,
                                      each_ref_fn fn, void *cb_data);

/* iterates all refs that match the specified glob pattern. */
int refs_for_each_glob_ref(struct ref_store *refs, each_ref_fn fn,
                           const char *pattern, void *cb_data);

int refs_for_each_glob_ref_in(struct ref_store *refs, each_ref_fn fn,
                              const char *pattern, const char *prefix, void *cb_data);

int refs_head_ref_namespaced(struct ref_store *refs, each_ref_fn fn, void *cb_data);

/*
 * references matching any pattern in "exclude_patterns" are omitted from the
 * result set on a best-effort basis.
 */
int refs_for_each_namespaced_ref(struct ref_store *refs,
                                 const char **exclude_patterns,
                                 each_ref_fn fn, void *cb_data);

/* can be used to learn about broken ref and symref */
int refs_for_each_rawref(struct ref_store *refs, each_ref_fn fn, void *cb_data);

/*
 * Iterates over all refs including root refs, i.e. pseudorefs and HEAD.
 */
int refs_for_each_include_root_refs(struct ref_store *refs, each_ref_fn fn,
                                    void *cb_data);

/*
 * Normalizes partial refs to their fully qualified form.
 * Will prepend <prefix> to the <pattern> if it doesn't start with 'refs/'.
 * <prefix> will default to 'refs/' if NULL.
 *
 * item.string will be set to the result.
 * item.util will be set to NULL if <pattern> contains glob characters, or
 * non-NULL if it doesn't.
 */
void normalize_glob_ref(struct string_list_item *item, const char *prefix,
                        const char *pattern);

static inline const char *has_glob_specials(const char *pattern)
{
        return strpbrk(pattern, "?*[");
}

void refs_warn_dangling_symref(struct ref_store *refs, FILE *fp,
                               const char *msg_fmt, const char *refname);
void refs_warn_dangling_symrefs(struct ref_store *refs, FILE *fp,
                                const char *msg_fmt, const struct string_list *refnames);

/*
 * Flags for controlling behaviour of pack_refs()
 * PACK_REFS_PRUNE: Prune loose refs after packing
 * PACK_REFS_AUTO: Pack refs on a best effort basis. The heuristics and end
 *                 result are decided by the ref backend. Backends may ignore
 *                 this flag and fall back to a normal repack.
 */
#define PACK_REFS_PRUNE (1 << 0)
#define PACK_REFS_AUTO  (1 << 1)

struct pack_refs_opts {
        unsigned int flags;
        struct ref_exclusions *exclusions;
        struct string_list *includes;
};

/*
 * Write a packed-refs file for the current repository.
 * flags: Combination of the above PACK_REFS_* flags.
 */
int refs_pack_refs(struct ref_store *refs, struct pack_refs_opts *opts);

/*
 * Setup reflog before using. Fill in err and return -1 on failure.
 */
int refs_create_reflog(struct ref_store *refs, const char *refname,
                       struct strbuf *err);

/**
 * Reads log for the value of ref during at_time (in which case "cnt" should be
 * negative) or the reflog "cnt" entries from the top (in which case "at_time"
 * should be 0).
 *
 * If we found the reflog entry in question, returns 0 (and details of the
 * entry can be found in the out-parameters).
 *
 * If we ran out of reflog entries, the out-parameters are filled with the
 * details of the oldest entry we did find, and the function returns 1. Note
 * that there is one important special case here! If the reflog was empty
 * and the caller asked for the 0-th cnt, we will return "1" but leave the
 * "oid" field untouched.
 **/
int read_ref_at(struct ref_store *refs,
                const char *refname, unsigned int flags,
                timestamp_t at_time, int cnt,
                struct object_id *oid, char **msg,
                timestamp_t *cutoff_time, int *cutoff_tz, int *cutoff_cnt);

/** Check if a particular reflog exists */
int refs_reflog_exists(struct ref_store *refs, const char *refname);

/*
 * Delete the specified reference. If old_oid is non-NULL, then
 * verify that the current value of the reference is old_oid before
 * deleting it. If old_oid is NULL, delete the reference if it
 * exists, regardless of its old value. It is an error for old_oid to
 * be null_oid. msg and flags are passed through to
 * ref_transaction_delete().
 */
int refs_delete_ref(struct ref_store *refs, const char *msg,
                    const char *refname,
                    const struct object_id *old_oid,
                    unsigned int flags);

/*
 * Delete the specified references. If there are any problems, emit
 * errors but attempt to keep going (i.e., the deletes are not done in
 * an all-or-nothing transaction). msg and flags are passed through to
 * ref_transaction_delete().
 */
int refs_delete_refs(struct ref_store *refs, const char *msg,
                     struct string_list *refnames, unsigned int flags);

/** Delete a reflog */
int refs_delete_reflog(struct ref_store *refs, const char *refname);

/*
 * Callback to process a reflog entry found by the iteration functions (see
 * below).
 *
 * The committer parameter is a single string, in the form
 * "$GIT_COMMITTER_NAME <$GIT_COMMITTER_EMAIL>" (without double quotes).
 *
 * The timestamp parameter gives the time when entry was created as the number
 * of seconds since the UNIX epoch.
 *
 * The tz parameter gives the timezone offset for the user who created
 * the reflog entry, and its value gives a positive or negative offset
 * from UTC.  Its absolute value is formed by multiplying the hour
 * part by 100 and adding the minute part.  For example, 1 hour ahead
 * of UTC, CET == "+0100", is represented as positive one hundred (not
 * postiive sixty).
 *
 * The msg parameter is a single complete line; a reflog message given
 * to refs_delete_ref, refs_update_ref, etc. is returned to the
 * callback normalized---each run of whitespaces are squashed into a
 * single whitespace, trailing whitespace, if exists, is trimmed, and
 * then a single LF is added at the end.
 *
 * The cb_data is a caller-supplied pointer given to the iterator
 * functions.
 */
typedef int each_reflog_ent_fn(
                struct object_id *old_oid, struct object_id *new_oid,
                const char *committer, timestamp_t timestamp,
                int tz, const char *msg, void *cb_data);

/* Iterate over reflog entries in the log for `refname`. */

/* oldest entry first */
int refs_for_each_reflog_ent(struct ref_store *refs, const char *refname,
                             each_reflog_ent_fn fn, void *cb_data);

/* youngest entry first */
int refs_for_each_reflog_ent_reverse(struct ref_store *refs,
                                     const char *refname,
                                     each_reflog_ent_fn fn,
                                     void *cb_data);

/*
 * The signature for the callback function for the refs_for_each_reflog()
 * functions below. The memory pointed to by the refname argument is only
 * guaranteed to be valid for the duration of a single callback invocation.
 */
typedef int each_reflog_fn(const char *refname, void *cb_data);

/*
 * Calls the specified function for each reflog file until it returns nonzero,
 * and returns the value. Reflog file order is unspecified.
 */
int refs_for_each_reflog(struct ref_store *refs, each_reflog_fn fn, void *cb_data);

#define REFNAME_ALLOW_ONELEVEL 1
#define REFNAME_REFSPEC_PATTERN 2

/*
 * Return 0 iff refname has the correct format for a refname according
 * to the rules described in Documentation/git-check-ref-format.txt.
 * If REFNAME_ALLOW_ONELEVEL is set in flags, then accept one-level
 * reference names.  If REFNAME_REFSPEC_PATTERN is set in flags, then
 * allow a single "*" wildcard character in the refspec. No leading or
 * repeated slashes are accepted.
 */
int check_refname_format(const char *refname, int flags);

/*
 * Apply the rules from check_refname_format, but mutate the result until it
 * is acceptable, and place the result in "out".
 */
void sanitize_refname_component(const char *refname, struct strbuf *out);

const char *prettify_refname(const char *refname);

char *refs_shorten_unambiguous_ref(struct ref_store *refs,
                                   const char *refname, int strict);

/** rename ref, return 0 on success **/
int refs_rename_ref(struct ref_store *refs, const char *oldref,
                    const char *newref, const char *logmsg);

/** copy ref, return 0 on success **/
int refs_copy_existing_ref(struct ref_store *refs, const char *oldref,
                    const char *newref, const char *logmsg);

int refs_update_symref(struct ref_store *refs, const char *refname,
                       const char *target, const char *logmsg);

enum action_on_err {
        UPDATE_REFS_MSG_ON_ERR,
        UPDATE_REFS_DIE_ON_ERR,
        UPDATE_REFS_QUIET_ON_ERR
};

/*
 * Begin a reference transaction.  The reference transaction must
 * be freed by calling ref_transaction_free().
 */
struct ref_transaction *ref_store_transaction_begin(struct ref_store *refs,
                                                    struct strbuf *err);

/*
 * Reference transaction updates
 *
 * The following four functions add a reference check or update to a
 * ref_transaction.  They have some common similar parameters:
 *
 *     transaction -- a pointer to an open ref_transaction, obtained
 *         from ref_transaction_begin().
 *
 *     refname -- the name of the reference to be affected.
 *
 *     new_oid -- the object ID that should be set to be the new value
 *         of the reference. Some functions allow this parameter to be
 *         NULL, meaning that the reference is not changed, or
 *         null_oid, meaning that the reference should be deleted. A
 *         copy of this value is made in the transaction.
 *
 *     old_oid -- the object ID that the reference must have before
 *         the update. Some functions allow this parameter to be NULL,
 *         meaning that the old value of the reference is not checked,
 *         or null_oid, meaning that the reference must not exist
 *         before the update. A copy of this value is made in the
 *         transaction.
 *
 *     new_target -- the target reference that the reference will be
 *         updated to point to. If the reference is a regular reference,
 *         it will be converted to a symbolic reference. Cannot be set
 *         together with `new_oid`. A copy of this value is made in the
 *         transaction.
 *
 *     old_target -- the reference that the reference must be pointing to.
 *         Canont be set together with `old_oid`. A copy of this value is
 *         made in the transaction.
 *
 *     flags -- flags affecting the update, passed to
 *         update_ref_lock(). Possible flags: REF_NO_DEREF,
 *         REF_FORCE_CREATE_REFLOG. See those constants for more
 *         information.
 *
 *     msg -- a message describing the change (for the reflog).
 *
 *     err -- a strbuf for receiving a description of any error that
 *         might have occurred.
 *
 * The functions make internal copies of refname and msg, so the
 * caller retains ownership of these parameters.
 *
 * The functions return 0 on success and non-zero on failure. A
 * failure means that the transaction as a whole has failed and needs
 * to be rolled back.
 */

/*
 * The following flags can be passed to ref_transaction_update() etc.
 * Internally, they are stored in `ref_update::flags`, along with some
 * internal flags.
 */

/*
 * Act on the ref directly; i.e., without dereferencing symbolic refs.
 * If this flag is not specified, then symbolic references are
 * dereferenced and the update is applied to the referent.
 */
#define REF_NO_DEREF (1 << 0)

/*
 * Force the creation of a reflog for this reference, even if it
 * didn't previously have a reflog.
 */
#define REF_FORCE_CREATE_REFLOG (1 << 1)

/*
 * Blindly write an object_id. This is useful for testing data corruption
 * scenarios.
 */
#define REF_SKIP_OID_VERIFICATION (1 << 10)

/*
 * Skip verifying refname. This is useful for testing data corruption scenarios.
 */
#define REF_SKIP_REFNAME_VERIFICATION (1 << 11)

/*
 * Skip creation of a reflog entry, even if it would have otherwise been
 * created.
 */
#define REF_SKIP_CREATE_REFLOG (1 << 12)

/*
 * Bitmask of all of the flags that are allowed to be passed in to
 * ref_transaction_update() and friends:
 */
#define REF_TRANSACTION_UPDATE_ALLOWED_FLAGS                                  \
        (REF_NO_DEREF | REF_FORCE_CREATE_REFLOG | REF_SKIP_OID_VERIFICATION | \
         REF_SKIP_REFNAME_VERIFICATION | REF_SKIP_CREATE_REFLOG)

/*
 * Add a reference update to transaction. `new_oid` is the value that
 * the reference should have after the update, or `null_oid` if it
 * should be deleted. If `new_oid` is NULL, then the reference is not
 * changed at all. `old_oid` is the value that the reference must have
 * before the update, or `null_oid` if it must not have existed
 * beforehand. The old value is checked after the lock is taken to
 * prevent races. If the old value doesn't agree with old_oid, the
 * whole transaction fails. If old_oid is NULL, then the previous
 * value is not checked. If `old_target` is not NULL, treat the reference
 * as a symbolic ref and validate that its target before the update is
 * `old_target`. If the `new_target` is not NULL, then the reference
 * will be updated to a symbolic ref which targets `new_target`.
 * Together, these allow us to update between regular refs and symrefs.
 *
 * See the above comment "Reference transaction updates" for more
 * information.
 */
int ref_transaction_update(struct ref_transaction *transaction,
                           const char *refname,
                           const struct object_id *new_oid,
                           const struct object_id *old_oid,
                           const char *new_target,
                           const char *old_target,
                           unsigned int flags, const char *msg,
                           struct strbuf *err);

/*
 * Add a reference creation to transaction. new_oid is the value that
 * the reference should have after the update; it must not be
 * null_oid. It is verified that the reference does not exist
 * already.
 *
 * See the above comment "Reference transaction updates" for more
 * information.
 */
int ref_transaction_create(struct ref_transaction *transaction,
                           const char *refname,
                           const struct object_id *new_oid,
                           const char *new_target,
                           unsigned int flags, const char *msg,
                           struct strbuf *err);

/*
 * Add a reference deletion to transaction. If old_oid is non-NULL,
 * then it holds the value that the reference should have had before
 * the update (which must not be null_oid).
 *
 * See the above comment "Reference transaction updates" for more
 * information.
 */
int ref_transaction_delete(struct ref_transaction *transaction,
                           const char *refname,
                           const struct object_id *old_oid,
                           const char *old_target,
                           unsigned int flags,
                           const char *msg,
                           struct strbuf *err);

/*
 * Verify, within a transaction, that refname has the value old_oid,
 * or, if old_oid is null_oid, then verify that the reference
 * doesn't exist. old_oid must be non-NULL.
 *
 * See the above comment "Reference transaction updates" for more
 * information.
 */
int ref_transaction_verify(struct ref_transaction *transaction,
                           const char *refname,
                           const struct object_id *old_oid,
                           const char *old_target,
                           unsigned int flags,
                           struct strbuf *err);

/* Naming conflict (for example, the ref names A and A/B conflict). */
#define TRANSACTION_NAME_CONFLICT -1
/* All other errors. */
#define TRANSACTION_GENERIC_ERROR -2

/*
 * Perform the preparatory stages of committing `transaction`. Acquire
 * any needed locks, check preconditions, etc.; basically, do as much
 * as possible to ensure that the transaction will be able to go
 * through, stopping just short of making any irrevocable or
 * user-visible changes. The updates that this function prepares can
 * be finished up by calling `ref_transaction_commit()` or rolled back
 * by calling `ref_transaction_abort()`.
 *
 * On success, return 0 and leave the transaction in "prepared" state.
 * On failure, abort the transaction, write an error message to `err`,
 * and return one of the `TRANSACTION_*` constants.
 *
 * Callers who don't need such fine-grained control over committing
 * reference transactions should just call `ref_transaction_commit()`.
 */
int ref_transaction_prepare(struct ref_transaction *transaction,
                            struct strbuf *err);

/*
 * Commit all of the changes that have been queued in transaction, as
 * atomically as possible. On success, return 0 and leave the
 * transaction in "closed" state. On failure, roll back the
 * transaction, write an error message to `err`, and return one of the
 * `TRANSACTION_*` constants
 */
int ref_transaction_commit(struct ref_transaction *transaction,
                           struct strbuf *err);

/*
 * Abort `transaction`, which has been begun and possibly prepared,
 * but not yet committed.
 */
int ref_transaction_abort(struct ref_transaction *transaction,
                          struct strbuf *err);

/*
 * Like ref_transaction_commit(), but optimized for creating
 * references when originally initializing a repository (e.g., by "git
 * clone"). It writes the new references directly to packed-refs
 * without locking the individual references.
 *
 * It is a bug to call this function when there might be other
 * processes accessing the repository or if there are existing
 * references that might conflict with the ones being created. All
 * old_oid values must either be absent or null_oid.
 */
int initial_ref_transaction_commit(struct ref_transaction *transaction,
                                   struct strbuf *err);

/*
 * Execute the given callback function for each of the reference updates which
 * have been queued in the given transaction. `old_oid` and `new_oid` may be
 * `NULL` pointers depending on whether the update has these object IDs set or
 * not.
 */
typedef void ref_transaction_for_each_queued_update_fn(const char *refname,
                                                       const struct object_id *old_oid,
                                                       const struct object_id *new_oid,
                                                       void *cb_data);
void ref_transaction_for_each_queued_update(struct ref_transaction *transaction,
                                            ref_transaction_for_each_queued_update_fn cb,
                                            void *cb_data);

/*
 * Free `*transaction` and all associated data.
 */
void ref_transaction_free(struct ref_transaction *transaction);

/**
 * Lock, update, and unlock a single reference. This function
 * basically does a transaction containing a single call to
 * ref_transaction_update(). The parameters to this function have the
 * same meaning as the corresponding parameters to
 * ref_transaction_update(). Handle errors as requested by the `onerr`
 * argument.
 */
int refs_update_ref(struct ref_store *refs, const char *msg, const char *refname,
                    const struct object_id *new_oid, const struct object_id *old_oid,
                    unsigned int flags, enum action_on_err onerr);

int parse_hide_refs_config(const char *var, const char *value, const char *,
                           struct strvec *);

/*
 * Check whether a ref is hidden. If no namespace is set, both the first and
 * the second parameter point to the full ref name. If a namespace is set and
 * the ref is inside that namespace, the first parameter is a pointer to the
 * name of the ref with the namespace prefix removed. If a namespace is set and
 * the ref is outside that namespace, the first parameter is NULL. The second
 * parameter always points to the full ref name.
 */
int ref_is_hidden(const char *, const char *, const struct strvec *);

/*
 * Returns an array of patterns to use as excluded_patterns, if none of the
 * hidden references use the token '!' or '^'.
 */
const char **hidden_refs_to_excludes(const struct strvec *hide_refs);

/* Is this a per-worktree ref living in the refs/ namespace? */
int is_per_worktree_ref(const char *refname);

/* Describes how a refname relates to worktrees */
enum ref_worktree_type {
        REF_WORKTREE_CURRENT, /* implicitly per worktree, eg. HEAD or
                                 refs/bisect/SOMETHING */
        REF_WORKTREE_MAIN, /* explicitly in main worktree, eg.
                              main-worktree/HEAD */
        REF_WORKTREE_OTHER, /* explicitly in named worktree, eg.
                               worktrees/bla/HEAD */
        REF_WORKTREE_SHARED, /* the default, eg. refs/heads/main */
};

/*
 * Parse a `maybe_worktree_ref` as a ref that possibly refers to a worktree ref
 * (ie. either REFNAME, main-worktree/REFNAME or worktree/WORKTREE/REFNAME). It
 * returns what kind of ref was found, and in case of REF_WORKTREE_OTHER, the
 * worktree name is returned in `worktree_name` (pointing into
 * `maybe_worktree_ref`) and `worktree_name_length`. The bare refname (the
 * refname stripped of prefixes) is returned in `bare_refname`. The
 * `worktree_name`, `worktree_name_length` and `bare_refname` arguments may be
 * NULL.
 */
enum ref_worktree_type parse_worktree_ref(const char *maybe_worktree_ref,
                                          const char **worktree_name,
                                          int *worktree_name_length,
                                          const char **bare_refname);

enum expire_reflog_flags {
        EXPIRE_REFLOGS_DRY_RUN = 1 << 0,
        EXPIRE_REFLOGS_UPDATE_REF = 1 << 1,
        EXPIRE_REFLOGS_REWRITE = 1 << 2,
};

/*
 * The following interface is used for reflog expiration. The caller
 * calls refs_reflog_expire(), supplying it with three callback functions,
 * of the following types. The callback functions define the
 * expiration policy that is desired.
 *
 * reflog_expiry_prepare_fn -- Called once after the reference is
 *     locked. Called with the OID of the locked reference.
 *
 * reflog_expiry_should_prune_fn -- Called once for each entry in the
 *     existing reflog. It should return true iff that entry should be
 *     pruned.
 *
 * reflog_expiry_cleanup_fn -- Called once before the reference is
 *     unlocked again.
 */
typedef void reflog_expiry_prepare_fn(const char *refname,
                                      const struct object_id *oid,
                                      void *cb_data);
typedef int reflog_expiry_should_prune_fn(struct object_id *ooid,
                                          struct object_id *noid,
                                          const char *email,
                                          timestamp_t timestamp, int tz,
                                          const char *message, void *cb_data);
typedef void reflog_expiry_cleanup_fn(void *cb_data);

/*
 * Expire reflog entries for the specified reference.
 * flags is a combination of the constants in
 * enum expire_reflog_flags. The three function pointers are described
 * above. On success, return zero.
 */
int refs_reflog_expire(struct ref_store *refs,
                       const char *refname,
                       unsigned int flags,
                       reflog_expiry_prepare_fn prepare_fn,
                       reflog_expiry_should_prune_fn should_prune_fn,
                       reflog_expiry_cleanup_fn cleanup_fn,
                       void *policy_cb_data);

struct ref_store *get_main_ref_store(struct repository *r);

/**
 * Submodules
 * ----------
 *
 * If you want to iterate the refs of a submodule you first need to add the
 * submodules object database. You can do this by a code-snippet like
 * this:
 *
 *      const char *path = "path/to/submodule"
 *      if (add_submodule_odb(path))
 *              die("Error submodule '%s' not populated.", path);
 *
 * `add_submodule_odb()` will return zero on success. If you
 * do not do this you will get an error for each ref that it does not point
 * to a valid object.
 *
 * Note: As a side-effect of this you cannot safely assume that all
 * objects you lookup are available in superproject. All submodule objects
 * will be available the same way as the superprojects objects.
 *
 * Example:
 * --------
 *
 * ----
 * static int handle_remote_ref(const char *refname,
 *              const unsigned char *sha1, int flags, void *cb_data)
 * {
 *      struct strbuf *output = cb_data;
 *      strbuf_addf(output, "%s\n", refname);
 *      return 0;
 * }
 *
 */

/*
 * Return the ref_store instance for the specified submodule. For the
 * main repository, use submodule==NULL; such a call cannot fail. For
 * a submodule, the submodule must exist and be a nonbare repository,
 * otherwise return NULL. If the requested reference store has not yet
 * been initialized, initialize it first.
 *
 * For backwards compatibility, submodule=="" is treated the same as
 * submodule==NULL.
 */
struct ref_store *repo_get_submodule_ref_store(struct repository *repo,
                                               const char *submodule);
struct ref_store *get_worktree_ref_store(const struct worktree *wt);

/*
 * Some of the names specified by refs have special meaning to Git.
 * Organize these namespaces in a comon 'ref_namespace' array for
 * reference from multiple places in the codebase.
 */

struct ref_namespace_info {
        const char *ref;
        enum decoration_type decoration;

        /*
         * If 'exact' is true, then we must match the 'ref' exactly.
         * Otherwise, use a prefix match.
         *
         * 'ref_updated' is for internal use. It represents whether the
         * 'ref' value was replaced from its original literal version.
         */
        unsigned exact:1,
                 ref_updated:1;
};

enum ref_namespace {
        NAMESPACE_HEAD,
        NAMESPACE_BRANCHES,
        NAMESPACE_TAGS,
        NAMESPACE_REMOTE_REFS,
        NAMESPACE_STASH,
        NAMESPACE_REPLACE,
        NAMESPACE_NOTES,
        NAMESPACE_PREFETCH,
        NAMESPACE_REWRITTEN,

        /* Must be last */
        NAMESPACE__COUNT
};

/* See refs.c for the contents of this array. */
extern struct ref_namespace_info ref_namespace[NAMESPACE__COUNT];

/*
 * Some ref namespaces can be modified by config values or environment
 * variables. Modify a namespace as specified by its ref_namespace key.
 */
void update_ref_namespace(enum ref_namespace namespace, char *ref);

/*
 * Check whether the provided name names a root reference. This function only
 * performs a syntactic check.
 *
 * A root ref is a reference that lives in the root of the reference hierarchy.
 * These references must conform to special syntax:
 *
 *   - Their name must be all-uppercase or underscores ("_").
 *
 *   - Their name must end with "_HEAD". As a special rule, "HEAD" is a root
 *     ref, as well.
 *
 *   - Their name may not contain a slash.
 *
 * There is a special set of irregular root refs that exist due to historic
 * reasons, only. This list shall not be expanded in the future:
 *
 *   - AUTO_MERGE
 *
 *   - BISECT_EXPECTED_REV
 *
 *   - NOTES_MERGE_PARTIAL
 *
 *   - NOTES_MERGE_REF
 *
 *   - MERGE_AUTOSTASH
 */
int is_root_ref(const char *refname);

/*
 * Pseudorefs are refs that have different semantics compared to
 * "normal" refs. These refs can thus not be stored in the ref backend,
 * but must always be accessed via the filesystem. The following refs
 * are pseudorefs:
 *
 * - FETCH_HEAD may contain multiple object IDs, and each one of them
 *   carries additional metadata like where it came from.
 *
 * - MERGE_HEAD may contain multiple object IDs when merging multiple
 *   heads.
 *
 * Reading, writing or deleting references must consistently go either
 * through the filesystem (pseudorefs) or through the reference
 * backend (normal ones).
 */
int is_pseudo_ref(const char *refname);

/*
 * The following flags can be passed to `repo_migrate_ref_storage_format()`:
 *
 *   - REPO_MIGRATE_REF_STORAGE_FORMAT_DRYRUN: perform a dry-run migration
 *     without touching the main repository. The result will be written into a
 *     temporary ref storage directory.
 */
#define REPO_MIGRATE_REF_STORAGE_FORMAT_DRYRUN (1 << 0)

/*
 * Migrate the ref storage format used by the repository to the
 * specified one.
 */
int repo_migrate_ref_storage_format(struct repository *repo,
                                    enum ref_storage_format format,
                                    unsigned int flags,
                                    struct strbuf *err);

/*
 * The following functions have been removed in Git v2.46 in favor of functions
 * that receive a `ref_store` as parameter. The intent of this section is
 * merely to help patch authors of in-flight series to have a reference what
 * they should be migrating to. The section will be removed in Git v2.47.
 */
#if 0
static char *resolve_refdup(const char *refname, int resolve_flags,
                            struct object_id *oid, int *flags)
{
        return refs_resolve_refdup(get_main_ref_store(the_repository),
                                   refname, resolve_flags,
                                   oid, flags);
}

static int read_ref_full(const char *refname, int resolve_flags,
                         struct object_id *oid, int *flags)
{
        return refs_read_ref_full(get_main_ref_store(the_repository), refname,
                                  resolve_flags, oid, flags);
}

static int read_ref(const char *refname, struct object_id *oid)
{
        return refs_read_ref(get_main_ref_store(the_repository), refname, oid);
}

static int ref_exists(const char *refname)
{
        return refs_ref_exists(get_main_ref_store(the_repository), refname);
}

static int for_each_tag_ref(each_ref_fn fn, void *cb_data)
{
        return refs_for_each_tag_ref(get_main_ref_store(the_repository), fn, cb_data);
}

static int for_each_branch_ref(each_ref_fn fn, void *cb_data)
{
        return refs_for_each_branch_ref(get_main_ref_store(the_repository), fn, cb_data);
}

static int for_each_remote_ref(each_ref_fn fn, void *cb_data)
{
        return refs_for_each_remote_ref(get_main_ref_store(the_repository), fn, cb_data);
}

static int head_ref_namespaced(each_ref_fn fn, void *cb_data)
{
        return refs_head_ref_namespaced(get_main_ref_store(the_repository),
                                        fn, cb_data);
}

static int for_each_glob_ref_in(each_ref_fn fn, const char *pattern,
                                const char *prefix, void *cb_data)
{
        return refs_for_each_glob_ref_in(get_main_ref_store(the_repository),
                                         fn, pattern, prefix, cb_data);
}

static int for_each_glob_ref(each_ref_fn fn, const char *pattern, void *cb_data)
{
        return refs_for_each_glob_ref(get_main_ref_store(the_repository),
                                      fn, pattern, cb_data);
}

static int delete_ref(const char *msg, const char *refname,
                      const struct object_id *old_oid, unsigned int flags)
{
        return refs_delete_ref(get_main_ref_store(the_repository), msg, refname,
                               old_oid, flags);
}

static struct ref_transaction *ref_transaction_begin(struct strbuf *err)
{
        return ref_store_transaction_begin(get_main_ref_store(the_repository), err);
}

static int update_ref(const char *msg, const char *refname,
                      const struct object_id *new_oid,
                      const struct object_id *old_oid,
                      unsigned int flags, enum action_on_err onerr)
{
        return refs_update_ref(get_main_ref_store(the_repository), msg, refname, new_oid,
                               old_oid, flags, onerr);
}

static char *shorten_unambiguous_ref(const char *refname, int strict)
{
        return refs_shorten_unambiguous_ref(get_main_ref_store(the_repository),
                                            refname, strict);
}

static int head_ref(each_ref_fn fn, void *cb_data)
{
        return refs_head_ref(get_main_ref_store(the_repository), fn, cb_data);
}

static int for_each_ref(each_ref_fn fn, void *cb_data)
{
        return refs_for_each_ref(get_main_ref_store(the_repository), fn, cb_data);
}

static int for_each_ref_in(const char *prefix, each_ref_fn fn, void *cb_data)
{
        return refs_for_each_ref_in(get_main_ref_store(the_repository), prefix, fn, cb_data);
}

static int for_each_fullref_in(const char *prefix,
                               const char **exclude_patterns,
                               each_ref_fn fn, void *cb_data)
{
        return refs_for_each_fullref_in(get_main_ref_store(the_repository),
                                        prefix, exclude_patterns, fn, cb_data);
}

static int for_each_namespaced_ref(const char **exclude_patterns,
                                   each_ref_fn fn, void *cb_data)
{
        return refs_for_each_namespaced_ref(get_main_ref_store(the_repository),
                                            exclude_patterns, fn, cb_data);
}

static int for_each_rawref(each_ref_fn fn, void *cb_data)
{
        return refs_for_each_rawref(get_main_ref_store(the_repository), fn, cb_data);
}

static const char *resolve_ref_unsafe(const char *refname, int resolve_flags,
                                      struct object_id *oid, int *flags)
{
        return refs_resolve_ref_unsafe(get_main_ref_store(the_repository), refname,
                                       resolve_flags, oid, flags);
}

static int create_symref(const char *ref_target, const char *refs_heads_master,
                         const char *logmsg)
{
        return refs_create_symref(get_main_ref_store(the_repository), ref_target,
                                  refs_heads_master, logmsg);
}

static int for_each_reflog(each_reflog_fn fn, void *cb_data)
{
        return refs_for_each_reflog(get_main_ref_store(the_repository), fn, cb_data);
}

static int for_each_reflog_ent_reverse(const char *refname, each_reflog_ent_fn fn,
                                       void *cb_data)
{
        return refs_for_each_reflog_ent_reverse(get_main_ref_store(the_repository),
                                                refname, fn, cb_data);
}

static int for_each_reflog_ent(const char *refname, each_reflog_ent_fn fn,
                               void *cb_data)
{
        return refs_for_each_reflog_ent(get_main_ref_store(the_repository), refname,
                                        fn, cb_data);
}

static int reflog_exists(const char *refname)
{
        return refs_reflog_exists(get_main_ref_store(the_repository), refname);
}

static int safe_create_reflog(const char *refname, struct strbuf *err)
{
        return refs_create_reflog(get_main_ref_store(the_repository), refname,
                                  err);
}

static int delete_reflog(const char *refname)
{
        return refs_delete_reflog(get_main_ref_store(the_repository), refname);
}

static int reflog_expire(const char *refname,
                         unsigned int flags,
                         reflog_expiry_prepare_fn prepare_fn,
                         reflog_expiry_should_prune_fn should_prune_fn,
                         reflog_expiry_cleanup_fn cleanup_fn,
                         void *policy_cb_data)
{
        return refs_reflog_expire(get_main_ref_store(the_repository),
                                  refname, flags,
                                  prepare_fn, should_prune_fn,
                                  cleanup_fn, policy_cb_data);
}

static int delete_refs(const char *msg, struct string_list *refnames,
                       unsigned int flags)
{
        return refs_delete_refs(get_main_ref_store(the_repository), msg, refnames, flags);
}

static int rename_ref(const char *oldref, const char *newref, const char *logmsg)
{
        return refs_rename_ref(get_main_ref_store(the_repository), oldref, newref, logmsg);
}

static int copy_existing_ref(const char *oldref, const char *newref, const char *logmsg)
{
        return refs_copy_existing_ref(get_main_ref_store(the_repository), oldref, newref, logmsg);
}
#endif

#endif /* REFS_H */