Merge branch 'ma/pager-per-subcommand-action'
[gitweb.git] / refs.c
diff --git a/refs.c b/refs.c
index 87dc82f1d87d6c0969b97f94035233bec0bc3729..fe4c59aa8b681e15abb75032d36605abce1940b4 100644 (file)
--- a/refs.c
+++ b/refs.c
@@ -3,11 +3,35 @@
  */
 
 #include "cache.h"
+#include "config.h"
+#include "hashmap.h"
 #include "lockfile.h"
+#include "iterator.h"
 #include "refs.h"
 #include "refs/refs-internal.h"
 #include "object.h"
 #include "tag.h"
+#include "submodule.h"
+#include "worktree.h"
+
+/*
+ * List of all available backends
+ */
+static struct ref_storage_be *refs_backends = &refs_be_files;
+
+static struct ref_storage_be *find_ref_storage_backend(const char *name)
+{
+       struct ref_storage_be *be;
+       for (be = refs_backends; be; be = be->next)
+               if (!strcmp(be->name, name))
+                       return be;
+       return NULL;
+}
+
+int ref_storage_backend_exists(const char *name)
+{
+       return find_ref_storage_backend(name) != NULL;
+}
 
 /*
  * How to handle various characters in refnames:
@@ -120,33 +144,53 @@ int check_refname_format(const char *refname, int flags)
 
 int refname_is_safe(const char *refname)
 {
-       if (starts_with(refname, "refs/")) {
+       const char *rest;
+
+       if (skip_prefix(refname, "refs/", &rest)) {
                char *buf;
                int result;
+               size_t restlen = strlen(rest);
+
+               /* rest must not be empty, or start or end with "/" */
+               if (!restlen || *rest == '/' || rest[restlen - 1] == '/')
+                       return 0;
 
-               buf = xmallocz(strlen(refname));
                /*
                 * Does the refname try to escape refs/?
                 * For example: refs/foo/../bar is safe but refs/foo/../../bar
                 * is not.
                 */
-               result = !normalize_path_copy(buf, refname + strlen("refs/"));
+               buf = xmallocz(restlen);
+               result = !normalize_path_copy(buf, rest) && !strcmp(buf, rest);
                free(buf);
                return result;
        }
-       while (*refname) {
+
+       do {
                if (!isupper(*refname) && *refname != '_')
                        return 0;
                refname++;
-       }
+       } while (*refname);
        return 1;
 }
 
+char *refs_resolve_refdup(struct ref_store *refs,
+                         const char *refname, int resolve_flags,
+                         unsigned char *sha1, int *flags)
+{
+       const char *result;
+
+       result = refs_resolve_ref_unsafe(refs, refname, resolve_flags,
+                                        sha1, flags);
+       return xstrdup_or_null(result);
+}
+
 char *resolve_refdup(const char *refname, int resolve_flags,
                     unsigned char *sha1, int *flags)
 {
-       return xstrdup_or_null(resolve_ref_unsafe(refname, resolve_flags,
-                                                 sha1, flags));
+       return refs_resolve_refdup(get_main_ref_store(),
+                                  refname, resolve_flags,
+                                  sha1, flags);
 }
 
 /* The argument to filter_refs */
@@ -156,13 +200,20 @@ struct ref_filter {
        void *cb_data;
 };
 
-int read_ref_full(const char *refname, int resolve_flags, unsigned char *sha1, int *flags)
+int refs_read_ref_full(struct ref_store *refs, const char *refname,
+                      int resolve_flags, unsigned char *sha1, int *flags)
 {
-       if (resolve_ref_unsafe(refname, resolve_flags, sha1, flags))
+       if (refs_resolve_ref_unsafe(refs, refname, resolve_flags, sha1, flags))
                return 0;
        return -1;
 }
 
+int read_ref_full(const char *refname, int resolve_flags, unsigned char *sha1, int *flags)
+{
+       return refs_read_ref_full(get_main_ref_store(), refname,
+                                 resolve_flags, sha1, flags);
+}
+
 int read_ref(const char *refname, unsigned char *sha1)
 {
        return read_ref_full(refname, RESOLVE_REF_READING, sha1, NULL);
@@ -179,7 +230,7 @@ static int filter_refs(const char *refname, const struct object_id *oid,
 {
        struct ref_filter *filter = (struct ref_filter *)data;
 
-       if (wildmatch(filter->pattern, refname, 0, NULL))
+       if (wildmatch(filter->pattern, refname, 0))
                return 0;
        return filter->fn(refname, oid, flags, filter->cb_data);
 }
@@ -257,34 +308,52 @@ void warn_dangling_symrefs(FILE *fp, const char *msg_fmt, const struct string_li
        for_each_rawref(warn_if_dangling_symref, &data);
 }
 
+int refs_for_each_tag_ref(struct ref_store *refs, each_ref_fn fn, void *cb_data)
+{
+       return refs_for_each_ref_in(refs, "refs/tags/", fn, cb_data);
+}
+
 int for_each_tag_ref(each_ref_fn fn, void *cb_data)
 {
-       return for_each_ref_in("refs/tags/", fn, cb_data);
+       return refs_for_each_tag_ref(get_main_ref_store(), fn, cb_data);
 }
 
 int for_each_tag_ref_submodule(const char *submodule, each_ref_fn fn, void *cb_data)
 {
-       return for_each_ref_in_submodule(submodule, "refs/tags/", fn, cb_data);
+       return refs_for_each_tag_ref(get_submodule_ref_store(submodule),
+                                    fn, cb_data);
+}
+
+int refs_for_each_branch_ref(struct ref_store *refs, each_ref_fn fn, void *cb_data)
+{
+       return refs_for_each_ref_in(refs, "refs/heads/", fn, cb_data);
 }
 
 int for_each_branch_ref(each_ref_fn fn, void *cb_data)
 {
-       return for_each_ref_in("refs/heads/", fn, cb_data);
+       return refs_for_each_branch_ref(get_main_ref_store(), fn, cb_data);
 }
 
 int for_each_branch_ref_submodule(const char *submodule, each_ref_fn fn, void *cb_data)
 {
-       return for_each_ref_in_submodule(submodule, "refs/heads/", fn, cb_data);
+       return refs_for_each_branch_ref(get_submodule_ref_store(submodule),
+                                       fn, cb_data);
+}
+
+int refs_for_each_remote_ref(struct ref_store *refs, each_ref_fn fn, void *cb_data)
+{
+       return refs_for_each_ref_in(refs, "refs/remotes/", fn, cb_data);
 }
 
 int for_each_remote_ref(each_ref_fn fn, void *cb_data)
 {
-       return for_each_ref_in("refs/remotes/", fn, cb_data);
+       return refs_for_each_remote_ref(get_main_ref_store(), fn, cb_data);
 }
 
 int for_each_remote_ref_submodule(const char *submodule, each_ref_fn fn, void *cb_data)
 {
-       return for_each_ref_in_submodule(submodule, "refs/remotes/", fn, cb_data);
+       return refs_for_each_remote_ref(get_submodule_ref_store(submodule),
+                                       fn, cb_data);
 }
 
 int head_ref_namespaced(each_ref_fn fn, void *cb_data)
@@ -338,11 +407,11 @@ int for_each_glob_ref(each_ref_fn fn, const char *pattern, void *cb_data)
 
 const char *prettify_refname(const char *name)
 {
-       return name + (
-               starts_with(name, "refs/heads/") ? 11 :
-               starts_with(name, "refs/tags/") ? 10 :
-               starts_with(name, "refs/remotes/") ? 13 :
-               0);
+       if (skip_prefix(name, "refs/heads/", &name) ||
+           skip_prefix(name, "refs/tags/", &name) ||
+           skip_prefix(name, "refs/remotes/", &name))
+               ; /* nothing */
+       return name;
 }
 
 static const char *ref_rev_parse_rules[] = {
@@ -377,7 +446,7 @@ int refname_match(const char *abbrev_name, const char *full_name)
 static char *substitute_branch_name(const char **string, int *len)
 {
        struct strbuf buf = STRBUF_INIT;
-       int ret = interpret_branch_name(*string, *len, &buf);
+       int ret = interpret_branch_name(*string, *len, &buf, 0);
 
        if (ret == *len) {
                size_t size;
@@ -392,32 +461,40 @@ static char *substitute_branch_name(const char **string, int *len)
 int dwim_ref(const char *str, int len, unsigned char *sha1, char **ref)
 {
        char *last_branch = substitute_branch_name(&str, &len);
+       int   refs_found  = expand_ref(str, len, sha1, ref);
+       free(last_branch);
+       return refs_found;
+}
+
+int expand_ref(const char *str, int len, unsigned char *sha1, char **ref)
+{
        const char **p, *r;
        int refs_found = 0;
+       struct strbuf fullref = STRBUF_INIT;
 
        *ref = NULL;
        for (p = ref_rev_parse_rules; *p; p++) {
-               char fullref[PATH_MAX];
                unsigned char sha1_from_ref[20];
                unsigned char *this_result;
                int flag;
 
                this_result = refs_found ? sha1_from_ref : sha1;
-               mksnpath(fullref, sizeof(fullref), *p, len, str);
-               r = resolve_ref_unsafe(fullref, RESOLVE_REF_READING,
+               strbuf_reset(&fullref);
+               strbuf_addf(&fullref, *p, len, str);
+               r = resolve_ref_unsafe(fullref.buf, RESOLVE_REF_READING,
                                       this_result, &flag);
                if (r) {
                        if (!refs_found++)
                                *ref = xstrdup(r);
                        if (!warn_ambiguous_refs)
                                break;
-               } else if ((flag & REF_ISSYMREF) && strcmp(fullref, "HEAD")) {
-                       warning("ignoring dangling symref %s.", fullref);
-               } else if ((flag & REF_ISBROKEN) && strchr(fullref, '/')) {
-                       warning("ignoring broken ref %s.", fullref);
+               } else if ((flag & REF_ISSYMREF) && strcmp(fullref.buf, "HEAD")) {
+                       warning("ignoring dangling symref %s.", fullref.buf);
+               } else if ((flag & REF_ISBROKEN) && strchr(fullref.buf, '/')) {
+                       warning("ignoring broken ref %s.", fullref.buf);
                }
        }
-       free(last_branch);
+       strbuf_release(&fullref);
        return refs_found;
 }
 
@@ -426,21 +503,22 @@ int dwim_log(const char *str, int len, unsigned char *sha1, char **log)
        char *last_branch = substitute_branch_name(&str, &len);
        const char **p;
        int logs_found = 0;
+       struct strbuf path = STRBUF_INIT;
 
        *log = NULL;
        for (p = ref_rev_parse_rules; *p; p++) {
                unsigned char hash[20];
-               char path[PATH_MAX];
                const char *ref, *it;
 
-               mksnpath(path, sizeof(path), *p, len, str);
-               ref = resolve_ref_unsafe(path, RESOLVE_REF_READING,
+               strbuf_reset(&path);
+               strbuf_addf(&path, *p, len, str);
+               ref = resolve_ref_unsafe(path.buf, RESOLVE_REF_READING,
                                         hash, NULL);
                if (!ref)
                        continue;
-               if (reflog_exists(path))
-                       it = path;
-               else if (strcmp(ref, path) && reflog_exists(ref))
+               if (reflog_exists(path.buf))
+                       it = path.buf;
+               else if (strcmp(ref, path.buf) && reflog_exists(ref))
                        it = ref;
                else
                        continue;
@@ -451,6 +529,7 @@ int dwim_log(const char *str, int len, unsigned char *sha1, char **log)
                if (!warn_ambiguous_refs)
                        break;
        }
+       strbuf_release(&path);
        free(last_branch);
        return logs_found;
 }
@@ -496,7 +575,7 @@ static int write_pseudoref(const char *pseudoref, const unsigned char *sha1,
        filename = git_path("%s", pseudoref);
        fd = hold_lock_file_for_update(&lock, filename, LOCK_DIE_ON_ERROR);
        if (fd < 0) {
-               strbuf_addf(err, "Could not open '%s' for writing: %s",
+               strbuf_addf(err, "could not open '%s' for writing: %s",
                            filename, strerror(errno));
                return -1;
        }
@@ -507,14 +586,14 @@ static int write_pseudoref(const char *pseudoref, const unsigned char *sha1,
                if (read_ref(pseudoref, actual_old_sha1))
                        die("could not read ref '%s'", pseudoref);
                if (hashcmp(actual_old_sha1, old_sha1)) {
-                       strbuf_addf(err, "Unexpected sha1 when writing %s", pseudoref);
+                       strbuf_addf(err, "unexpected sha1 when writing '%s'", pseudoref);
                        rollback_lock_file(&lock);
                        goto done;
                }
        }
 
        if (write_in_full(fd, buf.buf, buf.len) != buf.len) {
-               strbuf_addf(err, "Could not write to '%s'", filename);
+               strbuf_addf(err, "could not write to '%s'", filename);
                rollback_lock_file(&lock);
                goto done;
        }
@@ -558,19 +637,23 @@ static int delete_pseudoref(const char *pseudoref, const unsigned char *old_sha1
        return 0;
 }
 
-int delete_ref(const char *refname, const unsigned char *old_sha1,
-              unsigned int flags)
+int refs_delete_ref(struct ref_store *refs, const char *msg,
+                   const char *refname,
+                   const unsigned char *old_sha1,
+                   unsigned int flags)
 {
        struct ref_transaction *transaction;
        struct strbuf err = STRBUF_INIT;
 
-       if (ref_type(refname) == REF_TYPE_PSEUDOREF)
+       if (ref_type(refname) == REF_TYPE_PSEUDOREF) {
+               assert(refs == get_main_ref_store());
                return delete_pseudoref(refname, old_sha1);
+       }
 
-       transaction = ref_transaction_begin(&err);
+       transaction = ref_store_transaction_begin(refs, &err);
        if (!transaction ||
            ref_transaction_delete(transaction, refname, old_sha1,
-                                  flags, NULL, &err) ||
+                                  flags, msg, &err) ||
            ref_transaction_commit(transaction, &err)) {
                error("%s", err.buf);
                ref_transaction_free(transaction);
@@ -582,6 +665,13 @@ int delete_ref(const char *refname, const unsigned char *old_sha1,
        return 0;
 }
 
+int delete_ref(const char *msg, const char *refname,
+              const unsigned char *old_sha1, unsigned int flags)
+{
+       return refs_delete_ref(get_main_ref_store(), msg, refname,
+                              old_sha1, flags);
+}
+
 int copy_reflog_msg(char *buf, const char *msg)
 {
        char *cp = buf;
@@ -605,12 +695,17 @@ int copy_reflog_msg(char *buf, const char *msg)
 
 int should_autocreate_reflog(const char *refname)
 {
-       if (!log_all_ref_updates)
+       switch (log_all_ref_updates) {
+       case LOG_REFS_ALWAYS:
+               return 1;
+       case LOG_REFS_NORMAL:
+               return starts_with(refname, "refs/heads/") ||
+                       starts_with(refname, "refs/remotes/") ||
+                       starts_with(refname, "refs/notes/") ||
+                       !strcmp(refname, "HEAD");
+       default:
                return 0;
-       return starts_with(refname, "refs/heads/") ||
-               starts_with(refname, "refs/remotes/") ||
-               starts_with(refname, "refs/notes/") ||
-               !strcmp(refname, "HEAD");
+       }
 }
 
 int is_branch(const char *refname)
@@ -620,7 +715,7 @@ int is_branch(const char *refname)
 
 struct read_ref_at_cb {
        const char *refname;
-       unsigned long at_time;
+       timestamp_t at_time;
        int cnt;
        int reccnt;
        unsigned char *sha1;
@@ -629,15 +724,15 @@ struct read_ref_at_cb {
        unsigned char osha1[20];
        unsigned char nsha1[20];
        int tz;
-       unsigned long date;
+       timestamp_t date;
        char **msg;
-       unsigned long *cutoff_time;
+       timestamp_t *cutoff_time;
        int *cutoff_tz;
        int *cutoff_cnt;
 };
 
-static int read_ref_at_ent(unsigned char *osha1, unsigned char *nsha1,
-               const char *email, unsigned long timestamp, int tz,
+static int read_ref_at_ent(struct object_id *ooid, struct object_id *noid,
+               const char *email, timestamp_t timestamp, int tz,
                const char *message, void *cb_data)
 {
        struct read_ref_at_cb *cb = cb_data;
@@ -660,31 +755,31 @@ static int read_ref_at_ent(unsigned char *osha1, unsigned char *nsha1,
                 * hold the values for the previous record.
                 */
                if (!is_null_sha1(cb->osha1)) {
-                       hashcpy(cb->sha1, nsha1);
-                       if (hashcmp(cb->osha1, nsha1))
+                       hashcpy(cb->sha1, noid->hash);
+                       if (hashcmp(cb->osha1, noid->hash))
                                warning("Log for ref %s has gap after %s.",
                                        cb->refname, show_date(cb->date, cb->tz, DATE_MODE(RFC2822)));
                }
                else if (cb->date == cb->at_time)
-                       hashcpy(cb->sha1, nsha1);
-               else if (hashcmp(nsha1, cb->sha1))
+                       hashcpy(cb->sha1, noid->hash);
+               else if (hashcmp(noid->hash, cb->sha1))
                        warning("Log for ref %s unexpectedly ended on %s.",
                                cb->refname, show_date(cb->date, cb->tz,
                                                       DATE_MODE(RFC2822)));
-               hashcpy(cb->osha1, osha1);
-               hashcpy(cb->nsha1, nsha1);
+               hashcpy(cb->osha1, ooid->hash);
+               hashcpy(cb->nsha1, noid->hash);
                cb->found_it = 1;
                return 1;
        }
-       hashcpy(cb->osha1, osha1);
-       hashcpy(cb->nsha1, nsha1);
+       hashcpy(cb->osha1, ooid->hash);
+       hashcpy(cb->nsha1, noid->hash);
        if (cb->cnt > 0)
                cb->cnt--;
        return 0;
 }
 
-static int read_ref_at_ent_oldest(unsigned char *osha1, unsigned char *nsha1,
-                                 const char *email, unsigned long timestamp,
+static int read_ref_at_ent_oldest(struct object_id *ooid, struct object_id *noid,
+                                 const char *email, timestamp_t timestamp,
                                  int tz, const char *message, void *cb_data)
 {
        struct read_ref_at_cb *cb = cb_data;
@@ -697,16 +792,16 @@ static int read_ref_at_ent_oldest(unsigned char *osha1, unsigned char *nsha1,
                *cb->cutoff_tz = tz;
        if (cb->cutoff_cnt)
                *cb->cutoff_cnt = cb->reccnt;
-       hashcpy(cb->sha1, osha1);
+       hashcpy(cb->sha1, ooid->hash);
        if (is_null_sha1(cb->sha1))
-               hashcpy(cb->sha1, nsha1);
+               hashcpy(cb->sha1, noid->hash);
        /* We just want the first entry */
        return 1;
 }
 
-int read_ref_at(const char *refname, unsigned int flags, unsigned long at_time, int cnt,
+int read_ref_at(const char *refname, unsigned int flags, timestamp_t at_time, int cnt,
                unsigned char *sha1, char **msg,
-               unsigned long *cutoff_time, int *cutoff_tz, int *cutoff_cnt)
+               timestamp_t *cutoff_time, int *cutoff_tz, int *cutoff_cnt)
 {
        struct read_ref_at_cb cb;
 
@@ -723,7 +818,7 @@ int read_ref_at(const char *refname, unsigned int flags, unsigned long at_time,
        for_each_reflog_ent_reverse(refname, read_ref_at_ent, &cb);
 
        if (!cb.reccnt) {
-               if (flags & GET_SHA1_QUIETLY)
+               if (flags & GET_OID_QUIETLY)
                        exit(128);
                else
                        die("Log for %s is empty.", refname);
@@ -736,20 +831,42 @@ int read_ref_at(const char *refname, unsigned int flags, unsigned long at_time,
        return 1;
 }
 
-struct ref_transaction *ref_transaction_begin(struct strbuf *err)
+struct ref_transaction *ref_store_transaction_begin(struct ref_store *refs,
+                                                   struct strbuf *err)
 {
+       struct ref_transaction *tr;
        assert(err);
 
-       return xcalloc(1, sizeof(struct ref_transaction));
+       tr = xcalloc(1, sizeof(struct ref_transaction));
+       tr->ref_store = refs;
+       return tr;
+}
+
+struct ref_transaction *ref_transaction_begin(struct strbuf *err)
+{
+       return ref_store_transaction_begin(get_main_ref_store(), err);
 }
 
 void ref_transaction_free(struct ref_transaction *transaction)
 {
-       int i;
+       size_t i;
 
        if (!transaction)
                return;
 
+       switch (transaction->state) {
+       case REF_TRANSACTION_OPEN:
+       case REF_TRANSACTION_CLOSED:
+               /* OK */
+               break;
+       case REF_TRANSACTION_PREPARED:
+               die("BUG: free called on a prepared reference transaction");
+               break;
+       default:
+               die("BUG: unexpected reference transaction state");
+               break;
+       }
+
        for (i = 0; i < transaction->nr; i++) {
                free(transaction->updates[i]->msg);
                free(transaction->updates[i]);
@@ -758,13 +875,32 @@ void ref_transaction_free(struct ref_transaction *transaction)
        free(transaction);
 }
 
-static struct ref_update *add_update(struct ref_transaction *transaction,
-                                    const char *refname)
+struct ref_update *ref_transaction_add_update(
+               struct ref_transaction *transaction,
+               const char *refname, unsigned int flags,
+               const unsigned char *new_sha1,
+               const unsigned char *old_sha1,
+               const char *msg)
 {
        struct ref_update *update;
+
+       if (transaction->state != REF_TRANSACTION_OPEN)
+               die("BUG: update called for transaction that is not open");
+
+       if ((flags & REF_ISPRUNING) && !(flags & REF_NODEREF))
+               die("BUG: REF_ISPRUNING set without REF_NODEREF");
+
        FLEX_ALLOC_STR(update, refname, refname);
        ALLOC_GROW(transaction->updates, transaction->nr + 1, transaction->alloc);
        transaction->updates[transaction->nr++] = update;
+
+       update->flags = flags;
+
+       if (flags & REF_HAVE_NEW)
+               hashcpy(update->new_oid.hash, new_sha1);
+       if (flags & REF_HAVE_OLD)
+               hashcpy(update->old_oid.hash, old_sha1);
+       update->msg = xstrdup_or_null(msg);
        return update;
 }
 
@@ -775,32 +911,20 @@ int ref_transaction_update(struct ref_transaction *transaction,
                           unsigned int flags, const char *msg,
                           struct strbuf *err)
 {
-       struct ref_update *update;
-
        assert(err);
 
-       if (transaction->state != REF_TRANSACTION_OPEN)
-               die("BUG: update called for transaction that is not open");
-
-       if (new_sha1 && !is_null_sha1(new_sha1) &&
-           check_refname_format(refname, REFNAME_ALLOW_ONELEVEL)) {
-               strbuf_addf(err, "refusing to update ref with bad name %s",
+       if ((new_sha1 && !is_null_sha1(new_sha1)) ?
+           check_refname_format(refname, REFNAME_ALLOW_ONELEVEL) :
+           !refname_is_safe(refname)) {
+               strbuf_addf(err, "refusing to update ref with bad name '%s'",
                            refname);
                return -1;
        }
 
-       update = add_update(transaction, refname);
-       if (new_sha1) {
-               hashcpy(update->new_sha1, new_sha1);
-               flags |= REF_HAVE_NEW;
-       }
-       if (old_sha1) {
-               hashcpy(update->old_sha1, old_sha1);
-               flags |= REF_HAVE_OLD;
-       }
-       update->flags = flags;
-       if (msg)
-               update->msg = xstrdup(msg);
+       flags |= (new_sha1 ? REF_HAVE_NEW : 0) | (old_sha1 ? REF_HAVE_OLD : 0);
+
+       ref_transaction_add_update(transaction, refname, flags,
+                                  new_sha1, old_sha1, msg);
        return 0;
 }
 
@@ -842,18 +966,28 @@ int ref_transaction_verify(struct ref_transaction *transaction,
                                      flags, NULL, err);
 }
 
-int update_ref(const char *msg, const char *refname,
-              const unsigned char *new_sha1, const unsigned char *old_sha1,
+int update_ref_oid(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 update_ref(msg, refname, new_oid ? new_oid->hash : NULL,
+               old_oid ? old_oid->hash : NULL, flags, onerr);
+}
+
+int refs_update_ref(struct ref_store *refs, const char *msg,
+                   const char *refname, const unsigned char *new_sha1,
+                   const unsigned char *old_sha1, unsigned int flags,
+                   enum action_on_err onerr)
 {
        struct ref_transaction *t = NULL;
        struct strbuf err = STRBUF_INIT;
        int ret = 0;
 
        if (ref_type(refname) == REF_TYPE_PSEUDOREF) {
+               assert(refs == get_main_ref_store());
                ret = write_pseudoref(refname, new_sha1, old_sha1, &err);
        } else {
-               t = ref_transaction_begin(&err);
+               t = ref_store_transaction_begin(refs, &err);
                if (!t ||
                    ref_transaction_update(t, refname, new_sha1, old_sha1,
                                           flags, msg, &err) ||
@@ -884,12 +1018,22 @@ int update_ref(const char *msg, const char *refname,
        return 0;
 }
 
+int update_ref(const char *msg, const char *refname,
+              const unsigned char *new_sha1,
+              const unsigned char *old_sha1,
+              unsigned int flags, enum action_on_err onerr)
+{
+       return refs_update_ref(get_main_ref_store(), msg, refname, new_sha1,
+                              old_sha1, flags, onerr);
+}
+
 char *shorten_unambiguous_ref(const char *refname, int strict)
 {
        int i;
        static char **scanf_fmts;
        static int nr_rules;
        char *short_name;
+       struct strbuf resolved_buf = STRBUF_INIT;
 
        if (!nr_rules) {
                /*
@@ -906,7 +1050,7 @@ char *shorten_unambiguous_ref(const char *refname, int strict)
                        /* -2 for strlen("%.*s") - strlen("%s"); +1 for NUL */
                        total_len += strlen(ref_rev_parse_rules[nr_rules]) - 2 + 1;
 
-               scanf_fmts = xmalloc(st_add(st_mult(nr_rules, sizeof(char *)), total_len));
+               scanf_fmts = xmalloc(st_add(st_mult(sizeof(char *), nr_rules), total_len));
 
                offset = 0;
                for (i = 0; i < nr_rules; i++) {
@@ -948,7 +1092,6 @@ char *shorten_unambiguous_ref(const char *refname, int strict)
                 */
                for (j = 0; j < rules_to_fail; j++) {
                        const char *rule = ref_rev_parse_rules[j];
-                       char refname[PATH_MAX];
 
                        /* skip matched rule */
                        if (i == j)
@@ -959,9 +1102,10 @@ char *shorten_unambiguous_ref(const char *refname, int strict)
                         * (with this previous rule) to a valid ref
                         * read_ref() returns 0 on success
                         */
-                       mksnpath(refname, sizeof(refname),
-                                rule, short_name_len, short_name);
-                       if (ref_exists(refname))
+                       strbuf_reset(&resolved_buf);
+                       strbuf_addf(&resolved_buf, rule,
+                                   short_name_len, short_name);
+                       if (ref_exists(resolved_buf.buf))
                                break;
                }
 
@@ -969,10 +1113,13 @@ char *shorten_unambiguous_ref(const char *refname, int strict)
                 * short name is non-ambiguous if all previous rules
                 * haven't resolved to a valid ref
                 */
-               if (j == rules_to_fail)
+               if (j == rules_to_fail) {
+                       strbuf_release(&resolved_buf);
                        return short_name;
+               }
        }
 
+       strbuf_release(&resolved_buf);
        free(short_name);
        return xstrdup(refname);
 }
@@ -981,10 +1128,10 @@ static struct string_list *hide_refs;
 
 int parse_hide_refs_config(const char *var, const char *value, const char *section)
 {
+       const char *key;
        if (!strcmp("transfer.hiderefs", var) ||
-           /* NEEDSWORK: use parse_config_key() once both are merged */
-           (starts_with(var, section) && var[strlen(section)] == '.' &&
-            !strcmp(var + strlen(section), ".hiderefs"))) {
+           (!parse_config_key(var, section, NULL, NULL, &key) &&
+            !strcmp(key, "hiderefs"))) {
                char *ref;
                int len;
 
@@ -1013,7 +1160,7 @@ int ref_is_hidden(const char *refname, const char *refname_full)
                const char *match = hide_refs->items[i].string;
                const char *subject;
                int neg = 0;
-               int len;
+               const char *p;
 
                if (*match == '!') {
                        neg = 1;
@@ -1028,10 +1175,9 @@ int ref_is_hidden(const char *refname, const char *refname_full)
                }
 
                /* refname can be NULL when namespaces are used. */
-               if (!subject || !starts_with(subject, match))
-                       continue;
-               len = strlen(match);
-               if (!subject[len] || subject[len] == '/')
+               if (subject &&
+                   skip_prefix(subject, match, &p) &&
+                   (!*p || *p == '/'))
                        return !neg;
        }
        return 0;
@@ -1065,20 +1211,23 @@ const char *find_descendant_ref(const char *dirname,
        return NULL;
 }
 
-int rename_ref_available(const char *oldname, const char *newname)
+int refs_rename_ref_available(struct ref_store *refs,
+                             const char *old_refname,
+                             const char *new_refname)
 {
        struct string_list skip = STRING_LIST_INIT_NODUP;
        struct strbuf err = STRBUF_INIT;
-       int ret;
+       int ok;
 
-       string_list_insert(&skip, oldname);
-       ret = !verify_refname_available(newname, NULL, &skip, &err);
-       if (!ret)
+       string_list_insert(&skip, old_refname);
+       ok = !refs_verify_refname_available(refs, new_refname,
+                                           NULL, &skip, &err);
+       if (!ok)
                error("%s", err.buf);
 
        string_list_clear(&skip, 0);
        strbuf_release(&err);
-       return ret;
+       return ok;
 }
 
 int head_ref_submodule(const char *submodule, each_ref_fn fn, void *cb_data)
@@ -1104,19 +1253,75 @@ int head_ref(each_ref_fn fn, void *cb_data)
        return head_ref_submodule(NULL, fn, cb_data);
 }
 
+struct ref_iterator *refs_ref_iterator_begin(
+               struct ref_store *refs,
+               const char *prefix, int trim, int flags)
+{
+       struct ref_iterator *iter;
+
+       if (ref_paranoia < 0)
+               ref_paranoia = git_env_bool("GIT_REF_PARANOIA", 0);
+       if (ref_paranoia)
+               flags |= DO_FOR_EACH_INCLUDE_BROKEN;
+
+       iter = refs->be->iterator_begin(refs, prefix, flags);
+
+       /*
+        * `iterator_begin()` already takes care of prefix, but we
+        * might need to do some trimming:
+        */
+       if (trim)
+               iter = prefix_ref_iterator_begin(iter, "", trim);
+
+       return iter;
+}
+
+/*
+ * Call fn for each reference in the specified submodule for which the
+ * refname begins with prefix. If trim is non-zero, then trim that
+ * many characters off the beginning of each refname before passing
+ * the refname to fn. flags can be DO_FOR_EACH_INCLUDE_BROKEN to
+ * include broken references in the iteration. If fn ever returns a
+ * non-zero value, stop the iteration and return that value;
+ * otherwise, return 0.
+ */
+static int do_for_each_ref(struct ref_store *refs, const char *prefix,
+                          each_ref_fn fn, int trim, int flags, void *cb_data)
+{
+       struct ref_iterator *iter;
+
+       if (!refs)
+               return 0;
+
+       iter = refs_ref_iterator_begin(refs, prefix, trim, flags);
+
+       return do_for_each_ref_iterator(iter, fn, cb_data);
+}
+
+int refs_for_each_ref(struct ref_store *refs, each_ref_fn fn, void *cb_data)
+{
+       return do_for_each_ref(refs, "", fn, 0, 0, cb_data);
+}
+
 int for_each_ref(each_ref_fn fn, void *cb_data)
 {
-       return do_for_each_ref(NULL, "", fn, 0, 0, cb_data);
+       return refs_for_each_ref(get_main_ref_store(), fn, cb_data);
 }
 
 int for_each_ref_submodule(const char *submodule, each_ref_fn fn, void *cb_data)
 {
-       return do_for_each_ref(submodule, "", fn, 0, 0, cb_data);
+       return refs_for_each_ref(get_submodule_ref_store(submodule), fn, cb_data);
+}
+
+int refs_for_each_ref_in(struct ref_store *refs, const char *prefix,
+                        each_ref_fn fn, void *cb_data)
+{
+       return do_for_each_ref(refs, prefix, fn, strlen(prefix), 0, cb_data);
 }
 
 int for_each_ref_in(const char *prefix, each_ref_fn fn, void *cb_data)
 {
-       return do_for_each_ref(NULL, prefix, fn, strlen(prefix), 0, cb_data);
+       return refs_for_each_ref_in(get_main_ref_store(), prefix, fn, cb_data);
 }
 
 int for_each_fullref_in(const char *prefix, each_ref_fn fn, void *cb_data, unsigned int broken)
@@ -1125,19 +1330,35 @@ int for_each_fullref_in(const char *prefix, each_ref_fn fn, void *cb_data, unsig
 
        if (broken)
                flag = DO_FOR_EACH_INCLUDE_BROKEN;
-       return do_for_each_ref(NULL, prefix, fn, 0, flag, cb_data);
+       return do_for_each_ref(get_main_ref_store(),
+                              prefix, fn, 0, flag, cb_data);
 }
 
 int for_each_ref_in_submodule(const char *submodule, const char *prefix,
-               each_ref_fn fn, void *cb_data)
+                             each_ref_fn fn, void *cb_data)
 {
-       return do_for_each_ref(submodule, prefix, fn, strlen(prefix), 0, cb_data);
+       return refs_for_each_ref_in(get_submodule_ref_store(submodule),
+                                   prefix, fn, cb_data);
+}
+
+int for_each_fullref_in_submodule(const char *submodule, const char *prefix,
+                                 each_ref_fn fn, void *cb_data,
+                                 unsigned int broken)
+{
+       unsigned int flag = 0;
+
+       if (broken)
+               flag = DO_FOR_EACH_INCLUDE_BROKEN;
+       return do_for_each_ref(get_submodule_ref_store(submodule),
+                              prefix, fn, 0, flag, cb_data);
 }
 
 int for_each_replace_ref(each_ref_fn fn, void *cb_data)
 {
-       return do_for_each_ref(NULL, git_replace_ref_base, fn,
-                              strlen(git_replace_ref_base), 0, cb_data);
+       return do_for_each_ref(get_main_ref_store(),
+                              git_replace_ref_base, fn,
+                              strlen(git_replace_ref_base),
+                              0, cb_data);
 }
 
 int for_each_namespaced_ref(each_ref_fn fn, void *cb_data)
@@ -1145,20 +1366,35 @@ int for_each_namespaced_ref(each_ref_fn fn, void *cb_data)
        struct strbuf buf = STRBUF_INIT;
        int ret;
        strbuf_addf(&buf, "%srefs/", get_git_namespace());
-       ret = do_for_each_ref(NULL, buf.buf, fn, 0, 0, cb_data);
+       ret = do_for_each_ref(get_main_ref_store(),
+                             buf.buf, fn, 0, 0, cb_data);
        strbuf_release(&buf);
        return ret;
 }
 
-int for_each_rawref(each_ref_fn fn, void *cb_data)
+int refs_for_each_rawref(struct ref_store *refs, each_ref_fn fn, void *cb_data)
 {
-       return do_for_each_ref(NULL, "", fn, 0,
+       return do_for_each_ref(refs, "", fn, 0,
                               DO_FOR_EACH_INCLUDE_BROKEN, cb_data);
 }
 
+int for_each_rawref(each_ref_fn fn, void *cb_data)
+{
+       return refs_for_each_rawref(get_main_ref_store(), fn, cb_data);
+}
+
+int refs_read_raw_ref(struct ref_store *ref_store,
+                     const char *refname, unsigned char *sha1,
+                     struct strbuf *referent, unsigned int *type)
+{
+       return ref_store->be->read_raw_ref(ref_store, refname, sha1, referent, type);
+}
+
 /* This function needs to return a meaningful errno on failure */
-const char *resolve_ref_unsafe(const char *refname, int resolve_flags,
-                              unsigned char *sha1, int *flags)
+const char *refs_resolve_ref_unsafe(struct ref_store *refs,
+                                   const char *refname,
+                                   int resolve_flags,
+                                   unsigned char *sha1, int *flags)
 {
        static struct strbuf sb_refname = STRBUF_INIT;
        int unused_flags;
@@ -1190,7 +1426,8 @@ const char *resolve_ref_unsafe(const char *refname, int resolve_flags,
        for (symref_count = 0; symref_count < SYMREF_MAXDEPTH; symref_count++) {
                unsigned int read_flags = 0;
 
-               if (read_raw_ref(refname, sha1, &sb_refname, &read_flags)) {
+               if (refs_read_raw_ref(refs, refname,
+                                     sha1, &sb_refname, &read_flags)) {
                        *flags |= read_flags;
                        if (errno != ENOENT || (resolve_flags & RESOLVE_REF_READING))
                                return NULL;
@@ -1229,3 +1466,582 @@ const char *resolve_ref_unsafe(const char *refname, int resolve_flags,
        errno = ELOOP;
        return NULL;
 }
+
+/* backend functions */
+int refs_init_db(struct strbuf *err)
+{
+       struct ref_store *refs = get_main_ref_store();
+
+       return refs->be->init_db(refs, err);
+}
+
+const char *resolve_ref_unsafe(const char *refname, int resolve_flags,
+                              unsigned char *sha1, int *flags)
+{
+       return refs_resolve_ref_unsafe(get_main_ref_store(), refname,
+                                      resolve_flags, sha1, flags);
+}
+
+int resolve_gitlink_ref(const char *submodule, const char *refname,
+                       unsigned char *sha1)
+{
+       size_t len = strlen(submodule);
+       struct ref_store *refs;
+       int flags;
+
+       while (len && submodule[len - 1] == '/')
+               len--;
+
+       if (!len)
+               return -1;
+
+       if (submodule[len]) {
+               /* We need to strip off one or more trailing slashes */
+               char *stripped = xmemdupz(submodule, len);
+
+               refs = get_submodule_ref_store(stripped);
+               free(stripped);
+       } else {
+               refs = get_submodule_ref_store(submodule);
+       }
+
+       if (!refs)
+               return -1;
+
+       if (!refs_resolve_ref_unsafe(refs, refname, 0, sha1, &flags) ||
+           is_null_sha1(sha1))
+               return -1;
+       return 0;
+}
+
+struct ref_store_hash_entry
+{
+       struct hashmap_entry ent; /* must be the first member! */
+
+       struct ref_store *refs;
+
+       /* NUL-terminated identifier of the ref store: */
+       char name[FLEX_ARRAY];
+};
+
+static int ref_store_hash_cmp(const void *unused_cmp_data,
+                             const void *entry, const void *entry_or_key,
+                             const void *keydata)
+{
+       const struct ref_store_hash_entry *e1 = entry, *e2 = entry_or_key;
+       const char *name = keydata ? keydata : e2->name;
+
+       return strcmp(e1->name, name);
+}
+
+static struct ref_store_hash_entry *alloc_ref_store_hash_entry(
+               const char *name, struct ref_store *refs)
+{
+       struct ref_store_hash_entry *entry;
+
+       FLEX_ALLOC_STR(entry, name, name);
+       hashmap_entry_init(entry, strhash(name));
+       entry->refs = refs;
+       return entry;
+}
+
+/* A pointer to the ref_store for the main repository: */
+static struct ref_store *main_ref_store;
+
+/* A hashmap of ref_stores, stored by submodule name: */
+static struct hashmap submodule_ref_stores;
+
+/* A hashmap of ref_stores, stored by worktree id: */
+static struct hashmap worktree_ref_stores;
+
+/*
+ * Look up a ref store by name. If that ref_store hasn't been
+ * registered yet, return NULL.
+ */
+static struct ref_store *lookup_ref_store_map(struct hashmap *map,
+                                             const char *name)
+{
+       struct ref_store_hash_entry *entry;
+
+       if (!map->tablesize)
+               /* It's initialized on demand in register_ref_store(). */
+               return NULL;
+
+       entry = hashmap_get_from_hash(map, strhash(name), name);
+       return entry ? entry->refs : NULL;
+}
+
+/*
+ * Create, record, and return a ref_store instance for the specified
+ * gitdir.
+ */
+static struct ref_store *ref_store_init(const char *gitdir,
+                                       unsigned int flags)
+{
+       const char *be_name = "files";
+       struct ref_storage_be *be = find_ref_storage_backend(be_name);
+       struct ref_store *refs;
+
+       if (!be)
+               die("BUG: reference backend %s is unknown", be_name);
+
+       refs = be->init(gitdir, flags);
+       return refs;
+}
+
+struct ref_store *get_main_ref_store(void)
+{
+       if (main_ref_store)
+               return main_ref_store;
+
+       main_ref_store = ref_store_init(get_git_dir(), REF_STORE_ALL_CAPS);
+       return main_ref_store;
+}
+
+/*
+ * Associate a ref store with a name. It is a fatal error to call this
+ * function twice for the same name.
+ */
+static void register_ref_store_map(struct hashmap *map,
+                                  const char *type,
+                                  struct ref_store *refs,
+                                  const char *name)
+{
+       if (!map->tablesize)
+               hashmap_init(map, ref_store_hash_cmp, NULL, 0);
+
+       if (hashmap_put(map, alloc_ref_store_hash_entry(name, refs)))
+               die("BUG: %s ref_store '%s' initialized twice", type, name);
+}
+
+struct ref_store *get_submodule_ref_store(const char *submodule)
+{
+       struct strbuf submodule_sb = STRBUF_INIT;
+       struct ref_store *refs;
+       int ret;
+
+       if (!submodule || !*submodule) {
+               /*
+                * FIXME: This case is ideally not allowed. But that
+                * can't happen until we clean up all the callers.
+                */
+               return get_main_ref_store();
+       }
+
+       refs = lookup_ref_store_map(&submodule_ref_stores, submodule);
+       if (refs)
+               return refs;
+
+       strbuf_addstr(&submodule_sb, submodule);
+       ret = is_nonbare_repository_dir(&submodule_sb);
+       strbuf_release(&submodule_sb);
+       if (!ret)
+               return NULL;
+
+       ret = submodule_to_gitdir(&submodule_sb, submodule);
+       if (ret) {
+               strbuf_release(&submodule_sb);
+               return NULL;
+       }
+
+       /* assume that add_submodule_odb() has been called */
+       refs = ref_store_init(submodule_sb.buf,
+                             REF_STORE_READ | REF_STORE_ODB);
+       register_ref_store_map(&submodule_ref_stores, "submodule",
+                              refs, submodule);
+
+       strbuf_release(&submodule_sb);
+       return refs;
+}
+
+struct ref_store *get_worktree_ref_store(const struct worktree *wt)
+{
+       struct ref_store *refs;
+       const char *id;
+
+       if (wt->is_current)
+               return get_main_ref_store();
+
+       id = wt->id ? wt->id : "/";
+       refs = lookup_ref_store_map(&worktree_ref_stores, id);
+       if (refs)
+               return refs;
+
+       if (wt->id)
+               refs = ref_store_init(git_common_path("worktrees/%s", wt->id),
+                                     REF_STORE_ALL_CAPS);
+       else
+               refs = ref_store_init(get_git_common_dir(),
+                                     REF_STORE_ALL_CAPS);
+
+       if (refs)
+               register_ref_store_map(&worktree_ref_stores, "worktree",
+                                      refs, id);
+       return refs;
+}
+
+void base_ref_store_init(struct ref_store *refs,
+                        const struct ref_storage_be *be)
+{
+       refs->be = be;
+}
+
+/* backend functions */
+int refs_pack_refs(struct ref_store *refs, unsigned int flags)
+{
+       return refs->be->pack_refs(refs, flags);
+}
+
+int refs_peel_ref(struct ref_store *refs, const char *refname,
+                 unsigned char *sha1)
+{
+       return refs->be->peel_ref(refs, refname, sha1);
+}
+
+int peel_ref(const char *refname, unsigned char *sha1)
+{
+       return refs_peel_ref(get_main_ref_store(), refname, sha1);
+}
+
+int refs_create_symref(struct ref_store *refs,
+                      const char *ref_target,
+                      const char *refs_heads_master,
+                      const char *logmsg)
+{
+       return refs->be->create_symref(refs, ref_target,
+                                      refs_heads_master,
+                                      logmsg);
+}
+
+int create_symref(const char *ref_target, const char *refs_heads_master,
+                 const char *logmsg)
+{
+       return refs_create_symref(get_main_ref_store(), ref_target,
+                                 refs_heads_master, logmsg);
+}
+
+int ref_update_reject_duplicates(struct string_list *refnames,
+                                struct strbuf *err)
+{
+       size_t i, n = refnames->nr;
+
+       assert(err);
+
+       for (i = 1; i < n; i++) {
+               int cmp = strcmp(refnames->items[i - 1].string,
+                                refnames->items[i].string);
+
+               if (!cmp) {
+                       strbuf_addf(err,
+                                   "multiple updates for ref '%s' not allowed.",
+                                   refnames->items[i].string);
+                       return 1;
+               } else if (cmp > 0) {
+                       die("BUG: ref_update_reject_duplicates() received unsorted list");
+               }
+       }
+       return 0;
+}
+
+int ref_transaction_prepare(struct ref_transaction *transaction,
+                           struct strbuf *err)
+{
+       struct ref_store *refs = transaction->ref_store;
+
+       switch (transaction->state) {
+       case REF_TRANSACTION_OPEN:
+               /* Good. */
+               break;
+       case REF_TRANSACTION_PREPARED:
+               die("BUG: prepare called twice on reference transaction");
+               break;
+       case REF_TRANSACTION_CLOSED:
+               die("BUG: prepare called on a closed reference transaction");
+               break;
+       default:
+               die("BUG: unexpected reference transaction state");
+               break;
+       }
+
+       if (getenv(GIT_QUARANTINE_ENVIRONMENT)) {
+               strbuf_addstr(err,
+                             _("ref updates forbidden inside quarantine environment"));
+               return -1;
+       }
+
+       return refs->be->transaction_prepare(refs, transaction, err);
+}
+
+int ref_transaction_abort(struct ref_transaction *transaction,
+                         struct strbuf *err)
+{
+       struct ref_store *refs = transaction->ref_store;
+       int ret = 0;
+
+       switch (transaction->state) {
+       case REF_TRANSACTION_OPEN:
+               /* No need to abort explicitly. */
+               break;
+       case REF_TRANSACTION_PREPARED:
+               ret = refs->be->transaction_abort(refs, transaction, err);
+               break;
+       case REF_TRANSACTION_CLOSED:
+               die("BUG: abort called on a closed reference transaction");
+               break;
+       default:
+               die("BUG: unexpected reference transaction state");
+               break;
+       }
+
+       ref_transaction_free(transaction);
+       return ret;
+}
+
+int ref_transaction_commit(struct ref_transaction *transaction,
+                          struct strbuf *err)
+{
+       struct ref_store *refs = transaction->ref_store;
+       int ret;
+
+       switch (transaction->state) {
+       case REF_TRANSACTION_OPEN:
+               /* Need to prepare first. */
+               ret = ref_transaction_prepare(transaction, err);
+               if (ret)
+                       return ret;
+               break;
+       case REF_TRANSACTION_PREPARED:
+               /* Fall through to finish. */
+               break;
+       case REF_TRANSACTION_CLOSED:
+               die("BUG: commit called on a closed reference transaction");
+               break;
+       default:
+               die("BUG: unexpected reference transaction state");
+               break;
+       }
+
+       return refs->be->transaction_finish(refs, transaction, err);
+}
+
+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)
+{
+       const char *slash;
+       const char *extra_refname;
+       struct strbuf dirname = STRBUF_INIT;
+       struct strbuf referent = STRBUF_INIT;
+       struct object_id oid;
+       unsigned int type;
+       struct ref_iterator *iter;
+       int ok;
+       int ret = -1;
+
+       /*
+        * For the sake of comments in this function, suppose that
+        * refname is "refs/foo/bar".
+        */
+
+       assert(err);
+
+       strbuf_grow(&dirname, strlen(refname) + 1);
+       for (slash = strchr(refname, '/'); slash; slash = strchr(slash + 1, '/')) {
+               /* Expand dirname to the new prefix, not including the trailing slash: */
+               strbuf_add(&dirname, refname + dirname.len, slash - refname - dirname.len);
+
+               /*
+                * We are still at a leading dir of the refname (e.g.,
+                * "refs/foo"; if there is a reference with that name,
+                * it is a conflict, *unless* it is in skip.
+                */
+               if (skip && string_list_has_string(skip, dirname.buf))
+                       continue;
+
+               if (!refs_read_raw_ref(refs, dirname.buf, oid.hash, &referent, &type)) {
+                       strbuf_addf(err, "'%s' exists; cannot create '%s'",
+                                   dirname.buf, refname);
+                       goto cleanup;
+               }
+
+               if (extras && string_list_has_string(extras, dirname.buf)) {
+                       strbuf_addf(err, "cannot process '%s' and '%s' at the same time",
+                                   refname, dirname.buf);
+                       goto cleanup;
+               }
+       }
+
+       /*
+        * We are at the leaf of our refname (e.g., "refs/foo/bar").
+        * There is no point in searching for a reference with that
+        * name, because a refname isn't considered to conflict with
+        * itself. But we still need to check for references whose
+        * names are in the "refs/foo/bar/" namespace, because they
+        * *do* conflict.
+        */
+       strbuf_addstr(&dirname, refname + dirname.len);
+       strbuf_addch(&dirname, '/');
+
+       iter = refs_ref_iterator_begin(refs, dirname.buf, 0,
+                                      DO_FOR_EACH_INCLUDE_BROKEN);
+       while ((ok = ref_iterator_advance(iter)) == ITER_OK) {
+               if (skip &&
+                   string_list_has_string(skip, iter->refname))
+                       continue;
+
+               strbuf_addf(err, "'%s' exists; cannot create '%s'",
+                           iter->refname, refname);
+               ref_iterator_abort(iter);
+               goto cleanup;
+       }
+
+       if (ok != ITER_DONE)
+               die("BUG: error while iterating over references");
+
+       extra_refname = find_descendant_ref(dirname.buf, extras, skip);
+       if (extra_refname)
+               strbuf_addf(err, "cannot process '%s' and '%s' at the same time",
+                           refname, extra_refname);
+       else
+               ret = 0;
+
+cleanup:
+       strbuf_release(&referent);
+       strbuf_release(&dirname);
+       return ret;
+}
+
+int refs_for_each_reflog(struct ref_store *refs, each_ref_fn fn, void *cb_data)
+{
+       struct ref_iterator *iter;
+
+       iter = refs->be->reflog_iterator_begin(refs);
+
+       return do_for_each_ref_iterator(iter, fn, cb_data);
+}
+
+int for_each_reflog(each_ref_fn fn, void *cb_data)
+{
+       return refs_for_each_reflog(get_main_ref_store(), fn, cb_data);
+}
+
+int refs_for_each_reflog_ent_reverse(struct ref_store *refs,
+                                    const char *refname,
+                                    each_reflog_ent_fn fn,
+                                    void *cb_data)
+{
+       return refs->be->for_each_reflog_ent_reverse(refs, refname,
+                                                    fn, cb_data);
+}
+
+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(),
+                                               refname, fn, cb_data);
+}
+
+int refs_for_each_reflog_ent(struct ref_store *refs, const char *refname,
+                            each_reflog_ent_fn fn, void *cb_data)
+{
+       return refs->be->for_each_reflog_ent(refs, refname, fn, cb_data);
+}
+
+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(), refname,
+                                       fn, cb_data);
+}
+
+int refs_reflog_exists(struct ref_store *refs, const char *refname)
+{
+       return refs->be->reflog_exists(refs, refname);
+}
+
+int reflog_exists(const char *refname)
+{
+       return refs_reflog_exists(get_main_ref_store(), refname);
+}
+
+int refs_create_reflog(struct ref_store *refs, const char *refname,
+                      int force_create, struct strbuf *err)
+{
+       return refs->be->create_reflog(refs, refname, force_create, err);
+}
+
+int safe_create_reflog(const char *refname, int force_create,
+                      struct strbuf *err)
+{
+       return refs_create_reflog(get_main_ref_store(), refname,
+                                 force_create, err);
+}
+
+int refs_delete_reflog(struct ref_store *refs, const char *refname)
+{
+       return refs->be->delete_reflog(refs, refname);
+}
+
+int delete_reflog(const char *refname)
+{
+       return refs_delete_reflog(get_main_ref_store(), refname);
+}
+
+int refs_reflog_expire(struct ref_store *refs,
+                      const char *refname, const unsigned char *sha1,
+                      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->be->reflog_expire(refs, refname, sha1, flags,
+                                      prepare_fn, should_prune_fn,
+                                      cleanup_fn, policy_cb_data);
+}
+
+int reflog_expire(const char *refname, const unsigned char *sha1,
+                 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(),
+                                 refname, sha1, flags,
+                                 prepare_fn, should_prune_fn,
+                                 cleanup_fn, policy_cb_data);
+}
+
+int initial_ref_transaction_commit(struct ref_transaction *transaction,
+                                  struct strbuf *err)
+{
+       struct ref_store *refs = transaction->ref_store;
+
+       return refs->be->initial_transaction_commit(refs, transaction, err);
+}
+
+int refs_delete_refs(struct ref_store *refs, const char *msg,
+                    struct string_list *refnames, unsigned int flags)
+{
+       return refs->be->delete_refs(refs, msg, refnames, flags);
+}
+
+int delete_refs(const char *msg, struct string_list *refnames,
+               unsigned int flags)
+{
+       return refs_delete_refs(get_main_ref_store(), msg, refnames, flags);
+}
+
+int refs_rename_ref(struct ref_store *refs, const char *oldref,
+                   const char *newref, const char *logmsg)
+{
+       return refs->be->rename_ref(refs, oldref, newref, logmsg);
+}
+
+int rename_ref(const char *oldref, const char *newref, const char *logmsg)
+{
+       return refs_rename_ref(get_main_ref_store(), oldref, newref, logmsg);
+}