docs: introduce document to announce breaking changes

[git/gitster.git] / bundle-uri.c

#include "git-compat-util.h"
#include "bundle-uri.h"
#include "bundle.h"
#include "copy.h"
#include "environment.h"
#include "gettext.h"
#include "refs.h"
#include "run-command.h"
#include "hashmap.h"
#include "pkt-line.h"
#include "config.h"
#include "remote.h"

static struct {
        enum bundle_list_heuristic heuristic;
        const char *name;
} heuristics[BUNDLE_HEURISTIC__COUNT] = {
        { BUNDLE_HEURISTIC_NONE, ""},
        { BUNDLE_HEURISTIC_CREATIONTOKEN, "creationToken" },
};

static int compare_bundles(const void *hashmap_cmp_fn_data UNUSED,
                           const struct hashmap_entry *he1,
                           const struct hashmap_entry *he2,
                           const void *id)
{
        const struct remote_bundle_info *e1 =
                container_of(he1, const struct remote_bundle_info, ent);
        const struct remote_bundle_info *e2 =
                container_of(he2, const struct remote_bundle_info, ent);

        return strcmp(e1->id, id ? (const char *)id : e2->id);
}

void init_bundle_list(struct bundle_list *list)
{
        memset(list, 0, sizeof(*list));

        /* Implied defaults. */
        list->mode = BUNDLE_MODE_ALL;
        list->version = 1;

        hashmap_init(&list->bundles, compare_bundles, NULL, 0);
}

static int clear_remote_bundle_info(struct remote_bundle_info *bundle,
                                    void *data UNUSED)
{
        FREE_AND_NULL(bundle->id);
        FREE_AND_NULL(bundle->uri);
        FREE_AND_NULL(bundle->file);
        bundle->unbundled = 0;
        return 0;
}

void clear_bundle_list(struct bundle_list *list)
{
        if (!list)
                return;

        for_all_bundles_in_list(list, clear_remote_bundle_info, NULL);
        hashmap_clear_and_free(&list->bundles, struct remote_bundle_info, ent);
        free(list->baseURI);
}

int for_all_bundles_in_list(struct bundle_list *list,
                            bundle_iterator iter,
                            void *data)
{
        struct remote_bundle_info *info;
        struct hashmap_iter i;

        hashmap_for_each_entry(&list->bundles, &i, info, ent) {
                int result = iter(info, data);

                if (result)
                        return result;
        }

        return 0;
}

static int summarize_bundle(struct remote_bundle_info *info, void *data)
{
        FILE *fp = data;
        fprintf(fp, "[bundle \"%s\"]\n", info->id);
        fprintf(fp, "\turi = %s\n", info->uri);

        if (info->creationToken)
                fprintf(fp, "\tcreationToken = %"PRIu64"\n", info->creationToken);
        return 0;
}

void print_bundle_list(FILE *fp, struct bundle_list *list)
{
        const char *mode;

        switch (list->mode) {
        case BUNDLE_MODE_ALL:
                mode = "all";
                break;

        case BUNDLE_MODE_ANY:
                mode = "any";
                break;

        case BUNDLE_MODE_NONE:
        default:
                mode = "<unknown>";
        }

        fprintf(fp, "[bundle]\n");
        fprintf(fp, "\tversion = %d\n", list->version);
        fprintf(fp, "\tmode = %s\n", mode);

        if (list->heuristic) {
                int i;
                for (i = 0; i < BUNDLE_HEURISTIC__COUNT; i++) {
                        if (heuristics[i].heuristic == list->heuristic) {
                                printf("\theuristic = %s\n",
                                       heuristics[list->heuristic].name);
                                break;
                        }
                }
        }

        for_all_bundles_in_list(list, summarize_bundle, fp);
}

/**
 * Given a key-value pair, update the state of the given bundle list.
 * Returns 0 if the key-value pair is understood. Returns -1 if the key
 * is not understood or the value is malformed.
 */
static int bundle_list_update(const char *key, const char *value,
                              struct bundle_list *list)
{
        struct strbuf id = STRBUF_INIT;
        struct remote_bundle_info lookup = REMOTE_BUNDLE_INFO_INIT;
        struct remote_bundle_info *bundle;
        const char *subsection, *subkey;
        size_t subsection_len;

        if (parse_config_key(key, "bundle", &subsection, &subsection_len, &subkey))
                return -1;

        if (!subsection_len) {
                if (!strcmp(subkey, "version")) {
                        int version;
                        if (!git_parse_int(value, &version))
                                return -1;
                        if (version != 1)
                                return -1;

                        list->version = version;
                        return 0;
                }

                if (!strcmp(subkey, "mode")) {
                        if (!strcmp(value, "all"))
                                list->mode = BUNDLE_MODE_ALL;
                        else if (!strcmp(value, "any"))
                                list->mode = BUNDLE_MODE_ANY;
                        else
                                return -1;
                        return 0;
                }

                if (!strcmp(subkey, "heuristic")) {
                        int i;
                        for (i = 0; i < BUNDLE_HEURISTIC__COUNT; i++) {
                                if (heuristics[i].heuristic &&
                                    heuristics[i].name &&
                                    !strcmp(value, heuristics[i].name)) {
                                        list->heuristic = heuristics[i].heuristic;
                                        return 0;
                                }
                        }

                        /* Ignore unknown heuristics. */
                        return 0;
                }

                /* Ignore other unknown global keys. */
                return 0;
        }

        strbuf_add(&id, subsection, subsection_len);

        /*
         * Check for an existing bundle with this <id>, or create one
         * if necessary.
         */
        lookup.id = id.buf;
        hashmap_entry_init(&lookup.ent, strhash(lookup.id));
        if (!(bundle = hashmap_get_entry(&list->bundles, &lookup, ent, NULL))) {
                CALLOC_ARRAY(bundle, 1);
                bundle->id = strbuf_detach(&id, NULL);
                hashmap_entry_init(&bundle->ent, strhash(bundle->id));
                hashmap_add(&list->bundles, &bundle->ent);
        }
        strbuf_release(&id);

        if (!strcmp(subkey, "uri")) {
                if (bundle->uri)
                        return -1;
                bundle->uri = relative_url(list->baseURI, value, NULL);
                return 0;
        }

        if (!strcmp(subkey, "creationtoken")) {
                if (sscanf(value, "%"PRIu64, &bundle->creationToken) != 1)
                        warning(_("could not parse bundle list key %s with value '%s'"),
                                "creationToken", value);
                return 0;
        }

        /*
         * At this point, we ignore any information that we don't
         * understand, assuming it to be hints for a heuristic the client
         * does not currently understand.
         */
        return 0;
}

static int config_to_bundle_list(const char *key, const char *value,
                                 const struct config_context *ctx UNUSED,
                                 void *data)
{
        struct bundle_list *list = data;
        return bundle_list_update(key, value, list);
}

int bundle_uri_parse_config_format(const char *uri,
                                   const char *filename,
                                   struct bundle_list *list)
{
        int result;
        struct config_options opts = {
                .error_action = CONFIG_ERROR_ERROR,
        };

        if (!list->baseURI) {
                struct strbuf baseURI = STRBUF_INIT;
                strbuf_addstr(&baseURI, uri);

                /*
                 * If the URI does not end with a trailing slash, then
                 * remove the filename portion of the path. This is
                 * important for relative URIs.
                 */
                strbuf_strip_file_from_path(&baseURI);
                list->baseURI = strbuf_detach(&baseURI, NULL);
        }
        result = git_config_from_file_with_options(config_to_bundle_list,
                                                   filename, list,
                                                   CONFIG_SCOPE_UNKNOWN,
                                                   &opts);

        if (!result && list->mode == BUNDLE_MODE_NONE) {
                warning(_("bundle list at '%s' has no mode"), uri);
                result = 1;
        }

        return result;
}

static char *find_temp_filename(void)
{
        int fd;
        struct strbuf name = STRBUF_INIT;
        /*
         * Find a temporary filename that is available. This is briefly
         * racy, but unlikely to collide.
         */
        fd = odb_mkstemp(&name, "bundles/tmp_uri_XXXXXX");
        if (fd < 0) {
                warning(_("failed to create temporary file"));
                return NULL;
        }

        close(fd);
        unlink(name.buf);
        return strbuf_detach(&name, NULL);
}

static int download_https_uri_to_file(const char *file, const char *uri)
{
        int result = 0;
        struct child_process cp = CHILD_PROCESS_INIT;
        FILE *child_in = NULL, *child_out = NULL;
        struct strbuf line = STRBUF_INIT;
        int found_get = 0;

        strvec_pushl(&cp.args, "git-remote-https", uri, NULL);
        cp.err = -1;
        cp.in = -1;
        cp.out = -1;

        if (start_command(&cp))
                return 1;

        child_in = fdopen(cp.in, "w");
        if (!child_in) {
                result = 1;
                goto cleanup;
        }

        child_out = fdopen(cp.out, "r");
        if (!child_out) {
                result = 1;
                goto cleanup;
        }

        fprintf(child_in, "capabilities\n");
        fflush(child_in);

        while (!strbuf_getline(&line, child_out)) {
                if (!line.len)
                        break;
                if (!strcmp(line.buf, "get"))
                        found_get = 1;
        }
        strbuf_release(&line);

        if (!found_get) {
                result = error(_("insufficient capabilities"));
                goto cleanup;
        }

        fprintf(child_in, "get %s %s\n\n", uri, file);

cleanup:
        if (child_in)
                fclose(child_in);
        if (finish_command(&cp))
                return 1;
        if (child_out)
                fclose(child_out);
        return result;
}

static int copy_uri_to_file(const char *filename, const char *uri)
{
        const char *out;

        if (starts_with(uri, "https:") ||
            starts_with(uri, "http:"))
                return download_https_uri_to_file(filename, uri);

        if (skip_prefix(uri, "file://", &out))
                uri = out;

        /* Copy as a file */
        return copy_file(filename, uri, 0);
}

static int unbundle_from_file(struct repository *r, const char *file)
{
        int result = 0;
        int bundle_fd;
        struct bundle_header header = BUNDLE_HEADER_INIT;
        struct string_list_item *refname;
        struct strbuf bundle_ref = STRBUF_INIT;
        size_t bundle_prefix_len;

        if ((bundle_fd = read_bundle_header(file, &header)) < 0)
                return 1;

        /*
         * Skip the reachability walk here, since we will be adding
         * a reachable ref pointing to the new tips, which will reach
         * the prerequisite commits.
         */
        if ((result = unbundle(r, &header, bundle_fd, NULL,
                               VERIFY_BUNDLE_QUIET)))
                return 1;

        /*
         * Convert all refs/heads/ from the bundle into refs/bundles/
         * in the local repository.
         */
        strbuf_addstr(&bundle_ref, "refs/bundles/");
        bundle_prefix_len = bundle_ref.len;

        for_each_string_list_item(refname, &header.references) {
                struct object_id *oid = refname->util;
                struct object_id old_oid;
                const char *branch_name;
                int has_old;

                if (!skip_prefix(refname->string, "refs/heads/", &branch_name))
                        continue;

                strbuf_setlen(&bundle_ref, bundle_prefix_len);
                strbuf_addstr(&bundle_ref, branch_name);

                has_old = !read_ref(bundle_ref.buf, &old_oid);
                update_ref("fetched bundle", bundle_ref.buf, oid,
                           has_old ? &old_oid : NULL,
                           REF_SKIP_OID_VERIFICATION,
                           UPDATE_REFS_MSG_ON_ERR);
        }

        bundle_header_release(&header);
        return result;
}

struct bundle_list_context {
        struct repository *r;
        struct bundle_list *list;
        enum bundle_list_mode mode;
        int count;
        int depth;
};

/*
 * This early definition is necessary because we use indirect recursion:
 *
 * While iterating through a bundle list that was downloaded as part
 * of fetch_bundle_uri_internal(), iterator methods eventually call it
 * again, but with depth + 1.
 */
static int fetch_bundle_uri_internal(struct repository *r,
                                     struct remote_bundle_info *bundle,
                                     int depth,
                                     struct bundle_list *list);

static int download_bundle_to_file(struct remote_bundle_info *bundle, void *data)
{
        int res;
        struct bundle_list_context *ctx = data;

        if (ctx->mode == BUNDLE_MODE_ANY && ctx->count)
                return 0;

        res = fetch_bundle_uri_internal(ctx->r, bundle, ctx->depth + 1, ctx->list);

        /*
         * Only increment count if the download succeeded. If our mode is
         * BUNDLE_MODE_ANY, then we will want to try other URIs in the
         * list in case they work instead.
         */
        if (!res)
                ctx->count++;

        /*
         * To be opportunistic as possible, we continue iterating and
         * download as many bundles as we can, so we can apply the ones
         * that work, even in BUNDLE_MODE_ALL mode.
         */
        return 0;
}

struct bundles_for_sorting {
        struct remote_bundle_info **items;
        size_t alloc;
        size_t nr;
};

static int append_bundle(struct remote_bundle_info *bundle, void *data)
{
        struct bundles_for_sorting *list = data;
        list->items[list->nr++] = bundle;
        return 0;
}

/**
 * For use in QSORT() to get a list sorted by creationToken
 * in decreasing order.
 */
static int compare_creation_token_decreasing(const void *va, const void *vb)
{
        const struct remote_bundle_info * const *a = va;
        const struct remote_bundle_info * const *b = vb;

        if ((*a)->creationToken > (*b)->creationToken)
                return -1;
        if ((*a)->creationToken < (*b)->creationToken)
                return 1;
        return 0;
}

static int fetch_bundles_by_token(struct repository *r,
                                  struct bundle_list *list)
{
        int cur;
        int move_direction = 0;
        const char *creationTokenStr;
        uint64_t maxCreationToken = 0, newMaxCreationToken = 0;
        struct bundle_list_context ctx = {
                .r = r,
                .list = list,
                .mode = list->mode,
        };
        struct bundles_for_sorting bundles = {
                .alloc = hashmap_get_size(&list->bundles),
        };

        ALLOC_ARRAY(bundles.items, bundles.alloc);

        for_all_bundles_in_list(list, append_bundle, &bundles);

        if (!bundles.nr) {
                free(bundles.items);
                return 0;
        }

        QSORT(bundles.items, bundles.nr, compare_creation_token_decreasing);

        /*
         * If fetch.bundleCreationToken exists, parses to a uint64t, and
         * is not strictly smaller than the maximum creation token in the
         * bundle list, then do not download any bundles.
         */
        if (!repo_config_get_value(r,
                                   "fetch.bundlecreationtoken",
                                   &creationTokenStr) &&
            sscanf(creationTokenStr, "%"PRIu64, &maxCreationToken) == 1 &&
            bundles.items[0]->creationToken <= maxCreationToken) {
                free(bundles.items);
                return 0;
        }

        /*
         * Attempt to download and unbundle the minimum number of bundles by
         * creationToken in decreasing order. If we fail to unbundle (after
         * a successful download) then move to the next non-downloaded bundle
         * and attempt downloading. Once we succeed in applying a bundle,
         * move to the previous unapplied bundle and attempt to unbundle it
         * again.
         *
         * In the case of a fresh clone, we will likely download all of the
         * bundles before successfully unbundling the oldest one, then the
         * rest of the bundles unbundle successfully in increasing order
         * of creationToken.
         *
         * If there are existing objects, then this process may terminate
         * early when all required commits from "new" bundles exist in the
         * repo's object store.
         */
        cur = 0;
        while (cur >= 0 && cur < bundles.nr) {
                struct remote_bundle_info *bundle = bundles.items[cur];

                /*
                 * If we need to dig into bundles below the previous
                 * creation token value, then likely we are in an erroneous
                 * state due to missing or invalid bundles. Halt the process
                 * instead of continuing to download extra data.
                 */
                if (bundle->creationToken <= maxCreationToken)
                        break;

                if (!bundle->file) {
                        /*
                         * Not downloaded yet. Try downloading.
                         *
                         * Note that bundle->file is non-NULL if a download
                         * was attempted, even if it failed to download.
                         */
                        if (fetch_bundle_uri_internal(ctx.r, bundle, ctx.depth + 1, ctx.list)) {
                                /* Mark as unbundled so we do not retry. */
                                bundle->unbundled = 1;

                                /* Try looking deeper in the list. */
                                move_direction = 1;
                                goto move;
                        }

                        /* We expect bundles when using creationTokens. */
                        if (!is_bundle(bundle->file, 1)) {
                                warning(_("file downloaded from '%s' is not a bundle"),
                                        bundle->uri);
                                break;
                        }
                }

                if (bundle->file && !bundle->unbundled) {
                        /*
                         * This was downloaded, but not successfully
                         * unbundled. Try unbundling again.
                         */
                        if (unbundle_from_file(ctx.r, bundle->file)) {
                                /* Try looking deeper in the list. */
                                move_direction = 1;
                        } else {
                                /*
                                 * Succeeded in unbundle. Retry bundles
                                 * that previously failed to unbundle.
                                 */
                                move_direction = -1;
                                bundle->unbundled = 1;

                                if (bundle->creationToken > newMaxCreationToken)
                                        newMaxCreationToken = bundle->creationToken;
                        }
                }

                /*
                 * Else case: downloaded and unbundled successfully.
                 * Skip this by moving in the same direction as the
                 * previous step.
                 */

move:
                /* Move in the specified direction and repeat. */
                cur += move_direction;
        }

        /*
         * We succeed if the loop terminates because 'cur' drops below
         * zero. The other case is that we terminate because 'cur'
         * reaches the end of the list, so we have a failure no matter
         * which bundles we apply from the list.
         */
        if (cur < 0) {
                struct strbuf value = STRBUF_INIT;
                strbuf_addf(&value, "%"PRIu64"", newMaxCreationToken);
                if (repo_config_set_multivar_gently(ctx.r,
                                                    "fetch.bundleCreationToken",
                                                    value.buf, NULL, 0))
                        warning(_("failed to store maximum creation token"));

                strbuf_release(&value);
        }

        free(bundles.items);
        return cur >= 0;
}

static int download_bundle_list(struct repository *r,
                                struct bundle_list *local_list,
                                struct bundle_list *global_list,
                                int depth)
{
        struct bundle_list_context ctx = {
                .r = r,
                .list = global_list,
                .depth = depth + 1,
                .mode = local_list->mode,
        };

        return for_all_bundles_in_list(local_list, download_bundle_to_file, &ctx);
}

static int fetch_bundle_list_in_config_format(struct repository *r,
                                              struct bundle_list *global_list,
                                              struct remote_bundle_info *bundle,
                                              int depth)
{
        int result;
        struct bundle_list list_from_bundle;

        init_bundle_list(&list_from_bundle);

        if ((result = bundle_uri_parse_config_format(bundle->uri,
                                                     bundle->file,
                                                     &list_from_bundle)))
                goto cleanup;

        if (list_from_bundle.mode == BUNDLE_MODE_NONE) {
                warning(_("unrecognized bundle mode from URI '%s'"),
                        bundle->uri);
                result = -1;
                goto cleanup;
        }

        /*
         * If this list uses the creationToken heuristic, then the URIs
         * it advertises are expected to be bundles, not nested lists.
         * We can drop 'global_list' and 'depth'.
         */
        if (list_from_bundle.heuristic == BUNDLE_HEURISTIC_CREATIONTOKEN) {
                result = fetch_bundles_by_token(r, &list_from_bundle);
                global_list->heuristic = BUNDLE_HEURISTIC_CREATIONTOKEN;
        } else if ((result = download_bundle_list(r, &list_from_bundle,
                                           global_list, depth)))
                goto cleanup;

cleanup:
        clear_bundle_list(&list_from_bundle);
        return result;
}

/**
 * This limits the recursion on fetch_bundle_uri_internal() when following
 * bundle lists.
 */
static int max_bundle_uri_depth = 4;

/**
 * Recursively download all bundles advertised at the given URI
 * to files. If the file is a bundle, then add it to the given
 * 'list'. Otherwise, expect a bundle list and recurse on the
 * URIs in that list according to the list mode (ANY or ALL).
 */
static int fetch_bundle_uri_internal(struct repository *r,
                                     struct remote_bundle_info *bundle,
                                     int depth,
                                     struct bundle_list *list)
{
        int result = 0;
        struct remote_bundle_info *bcopy;

        if (depth >= max_bundle_uri_depth) {
                warning(_("exceeded bundle URI recursion limit (%d)"),
                        max_bundle_uri_depth);
                return -1;
        }

        if (!bundle->file &&
            !(bundle->file = find_temp_filename())) {
                result = -1;
                goto cleanup;
        }

        if ((result = copy_uri_to_file(bundle->file, bundle->uri))) {
                warning(_("failed to download bundle from URI '%s'"), bundle->uri);
                goto cleanup;
        }

        if ((result = !is_bundle(bundle->file, 1))) {
                result = fetch_bundle_list_in_config_format(
                                r, list, bundle, depth);
                if (result)
                        warning(_("file at URI '%s' is not a bundle or bundle list"),
                                bundle->uri);
                goto cleanup;
        }

        /* Copy the bundle and insert it into the global list. */
        CALLOC_ARRAY(bcopy, 1);
        bcopy->id = xstrdup(bundle->id);
        bcopy->file = xstrdup(bundle->file);
        hashmap_entry_init(&bcopy->ent, strhash(bcopy->id));
        hashmap_add(&list->bundles, &bcopy->ent);

cleanup:
        if (result && bundle->file)
                unlink(bundle->file);
        return result;
}

/**
 * This loop iterator breaks the loop with nonzero return code on the
 * first successful unbundling of a bundle.
 */
static int attempt_unbundle(struct remote_bundle_info *info, void *data)
{
        struct repository *r = data;

        if (!info->file || info->unbundled)
                return 0;

        if (!unbundle_from_file(r, info->file)) {
                info->unbundled = 1;
                return 1;
        }

        return 0;
}

static int unbundle_all_bundles(struct repository *r,
                                struct bundle_list *list)
{
        /*
         * Iterate through all bundles looking for ones that can
         * successfully unbundle. If any succeed, then perhaps another
         * will succeed in the next attempt.
         *
         * Keep in mind that a non-zero result for the loop here means
         * the loop terminated early on a successful unbundling, which
         * signals that we can try again.
         */
        while (for_all_bundles_in_list(list, attempt_unbundle, r)) ;

        return 0;
}

static int unlink_bundle(struct remote_bundle_info *info, void *data UNUSED)
{
        if (info->file)
                unlink_or_warn(info->file);
        return 0;
}

int fetch_bundle_uri(struct repository *r, const char *uri,
                     int *has_heuristic)
{
        int result;
        struct bundle_list list;
        struct remote_bundle_info bundle = {
                .uri = xstrdup(uri),
                .id = xstrdup(""),
        };

        init_bundle_list(&list);

        /*
         * Do not fetch an empty bundle URI. An empty bundle URI
         * could signal that a configured bundle URI has been disabled.
         */
        if (!*uri) {
                result = 0;
                goto cleanup;
        }

        /* If a bundle is added to this global list, then it is required. */
        list.mode = BUNDLE_MODE_ALL;

        if ((result = fetch_bundle_uri_internal(r, &bundle, 0, &list)))
                goto cleanup;

        result = unbundle_all_bundles(r, &list);

cleanup:
        if (has_heuristic)
                *has_heuristic = (list.heuristic != BUNDLE_HEURISTIC_NONE);
        for_all_bundles_in_list(&list, unlink_bundle, NULL);
        clear_bundle_list(&list);
        clear_remote_bundle_info(&bundle, NULL);
        return result;
}

int fetch_bundle_list(struct repository *r, struct bundle_list *list)
{
        int result;
        struct bundle_list global_list;

        /*
         * If the creationToken heuristic is used, then the URIs
         * advertised by 'list' are not nested lists and instead
         * direct bundles. We do not need to use global_list.
         */
        if (list->heuristic == BUNDLE_HEURISTIC_CREATIONTOKEN)
                return fetch_bundles_by_token(r, list);

        init_bundle_list(&global_list);

        /* If a bundle is added to this global list, then it is required. */
        global_list.mode = BUNDLE_MODE_ALL;

        if ((result = download_bundle_list(r, list, &global_list, 0)))
                goto cleanup;

        if (list->heuristic == BUNDLE_HEURISTIC_CREATIONTOKEN)
                result = fetch_bundles_by_token(r, list);
        else
                result = unbundle_all_bundles(r, &global_list);

cleanup:
        for_all_bundles_in_list(&global_list, unlink_bundle, NULL);
        clear_bundle_list(&global_list);
        return result;
}

/**
 * API for serve.c.
 */

int bundle_uri_advertise(struct repository *r, struct strbuf *value UNUSED)
{
        static int advertise_bundle_uri = -1;

        if (advertise_bundle_uri != -1)
                goto cached;

        advertise_bundle_uri = 0;
        repo_config_get_maybe_bool(r, "uploadpack.advertisebundleuris", &advertise_bundle_uri);

cached:
        return advertise_bundle_uri;
}

static int config_to_packet_line(const char *key, const char *value,
                                 const struct config_context *ctx UNUSED,
                                 void *data)
{
        struct packet_reader *writer = data;

        if (starts_with(key, "bundle."))
                packet_write_fmt(writer->fd, "%s=%s", key, value);

        return 0;
}

int bundle_uri_command(struct repository *r,
                       struct packet_reader *request)
{
        struct packet_writer writer;
        packet_writer_init(&writer, 1);

        while (packet_reader_read(request) == PACKET_READ_NORMAL)
                die(_("bundle-uri: unexpected argument: '%s'"), request->line);
        if (request->status != PACKET_READ_FLUSH)
                die(_("bundle-uri: expected flush after arguments"));

        /*
         * Read all "bundle.*" config lines to the client as key=value
         * packet lines.
         */
        repo_config(r, config_to_packet_line, &writer);

        packet_writer_flush(&writer);

        return 0;
}

/**
 * General API for {transport,connect}.c etc.
 */
int bundle_uri_parse_line(struct bundle_list *list, const char *line)
{
        int result;
        const char *equals;
        struct strbuf key = STRBUF_INIT;

        if (!strlen(line))
                return error(_("bundle-uri: got an empty line"));

        equals = strchr(line, '=');

        if (!equals)
                return error(_("bundle-uri: line is not of the form 'key=value'"));
        if (line == equals || !*(equals + 1))
                return error(_("bundle-uri: line has empty key or value"));

        strbuf_add(&key, line, equals - line);
        result = bundle_list_update(key.buf, equals + 1, list);
        strbuf_release(&key);

        return result;
}