git-am: add am.threeWay config variable
[gitweb.git] / refs.c
diff --git a/refs.c b/refs.c
index 07f8847e6d78423a4b70b9e66d6ddfe97845e421..ce8cd8d45001d627b58dc2bbb2c6bfdc3bc18888 100644 (file)
--- a/refs.c
+++ b/refs.c
@@ -6,6 +6,13 @@
 #include "dir.h"
 #include "string-list.h"
 
+struct ref_lock {
+       char *ref_name;
+       char *orig_ref_name;
+       struct lock_file *lk;
+       struct object_id old_oid;
+};
+
 /*
  * How to handle various characters in refnames:
  * 0: An acceptable character for refs
@@ -26,10 +33,35 @@ static unsigned char refname_disposition[256] = {
 };
 
 /*
- * Used as a flag to ref_transaction_delete when a loose ref is being
+ * Flag passed to lock_ref_sha1_basic() telling it to tolerate broken
+ * refs (i.e., because the reference is about to be deleted anyway).
+ */
+#define REF_DELETING   0x02
+
+/*
+ * Used as a flag in ref_update::flags when a loose ref is being
  * pruned.
  */
-#define REF_ISPRUNING  0x0100
+#define REF_ISPRUNING  0x04
+
+/*
+ * Used as a flag in ref_update::flags when the reference should be
+ * updated to new_sha1.
+ */
+#define REF_HAVE_NEW   0x08
+
+/*
+ * Used as a flag in ref_update::flags when old_sha1 should be
+ * checked.
+ */
+#define REF_HAVE_OLD   0x10
+
+/*
+ * Used as a flag in ref_update::flags when the lockfile needs to be
+ * committed.
+ */
+#define REF_NEEDS_COMMIT 0x20
+
 /*
  * Try to read one refname component from the front of refname.
  * Return the length of the component found, or -1 if the component is
@@ -129,7 +161,7 @@ struct ref_value {
         * null.  If REF_ISSYMREF, then this is the name of the object
         * referred to by the last reference in the symlink chain.
         */
-       unsigned char sha1[20];
+       struct object_id oid;
 
        /*
         * If REF_KNOWS_PEELED, then this field holds the peeled value
@@ -137,7 +169,7 @@ struct ref_value {
         * be peelable.  See the documentation for peel_ref() for an
         * exact definition of "peelable".
         */
-       unsigned char peeled[20];
+       struct object_id peeled;
 };
 
 struct ref_cache;
@@ -236,7 +268,7 @@ struct ref_dir {
  * presence of an empty subdirectory does not block the creation of a
  * similarly-named reference.  (The fact that reference names with the
  * same leading components can conflict *with each other* is a
- * separate issue that is regulated by is_refname_available().)
+ * separate issue that is regulated by verify_refname_available().)
  *
  * Please note that the name field contains the fully-qualified
  * reference (or subdirectory) name.  Space could be saved by only
@@ -317,12 +349,10 @@ static struct ref_entry *create_ref_entry(const char *refname,
        if (check_name &&
            check_refname_format(refname, REFNAME_ALLOW_ONELEVEL))
                die("Reference has invalid format: '%s'", refname);
-       if (!check_name && !refname_is_safe(refname))
-               die("Reference has invalid name: '%s'", refname);
        len = strlen(refname) + 1;
        ref = xmalloc(sizeof(struct ref_entry) + len);
-       hashcpy(ref->u.value.sha1, sha1);
-       hashclr(ref->u.value.peeled);
+       hashcpy(ref->u.value.oid.hash, sha1);
+       oidclr(&ref->u.value.peeled);
        memcpy(ref->name, refname, len);
        ref->flag = flag;
        return ref;
@@ -596,7 +626,7 @@ static int is_dup_ref(const struct ref_entry *ref1, const struct ref_entry *ref2
                /* This is impossible by construction */
                die("Reference directory conflict: %s", ref1->name);
 
-       if (hashcmp(ref1->u.value.sha1, ref2->u.value.sha1))
+       if (oidcmp(&ref1->u.value.oid, &ref2->u.value.oid))
                die("Duplicated ref, and SHA1s don't match: %s", ref1->name);
 
        warning("Duplicated ref: %s", ref1->name);
@@ -644,7 +674,7 @@ static int ref_resolves_to_object(struct ref_entry *entry)
 {
        if (entry->flag & REF_ISBROKEN)
                return 0;
-       if (!has_sha1_file(entry->u.value.sha1)) {
+       if (!has_sha1_file(entry->u.value.oid.hash)) {
                error("%s does not point to a valid object!", entry->name);
                return 0;
        }
@@ -692,7 +722,7 @@ static int do_one_ref(struct ref_entry *entry, void *cb_data)
        /* Store the old value, in case this is a recursive call: */
        old_current_ref = current_ref;
        current_ref = entry;
-       retval = data->fn(entry->name + data->trim, entry->u.value.sha1,
+       retval = data->fn(entry->name + data->trim, &entry->u.value.oid,
                          entry->flag, data->cb_data);
        current_ref = old_current_ref;
        return retval;
@@ -814,121 +844,181 @@ static void prime_ref_dir(struct ref_dir *dir)
        }
 }
 
-static int entry_matches(struct ref_entry *entry, const struct string_list *list)
-{
-       return list && string_list_has_string(list, entry->name);
-}
-
 struct nonmatching_ref_data {
        const struct string_list *skip;
-       struct ref_entry *found;
+       const char *conflicting_refname;
 };
 
 static int nonmatching_ref_fn(struct ref_entry *entry, void *vdata)
 {
        struct nonmatching_ref_data *data = vdata;
 
-       if (entry_matches(entry, data->skip))
+       if (data->skip && string_list_has_string(data->skip, entry->name))
                return 0;
 
-       data->found = entry;
+       data->conflicting_refname = entry->name;
        return 1;
 }
 
-static void report_refname_conflict(struct ref_entry *entry,
-                                   const char *refname)
-{
-       error("'%s' exists; cannot create '%s'", entry->name, refname);
-}
-
 /*
- * Return true iff a reference named refname could be created without
- * conflicting with the name of an existing reference in dir.  If
- * skip is non-NULL, ignore potential conflicts with refs in skip
- * (e.g., because they are scheduled for deletion in the same
- * operation).
+ * Return 0 if a reference named refname could be created without
+ * conflicting with the name of an existing reference in dir.
+ * 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".
+ * leading components of the other; e.g., "refs/foo/bar" conflicts
+ * with both "refs/foo" and with "refs/foo/bar/baz" but not with
+ * "refs/foo/bar" or "refs/foo/barbados".
  *
- * skip must be sorted.
+ * extras and skip must be sorted.
  */
-static int is_refname_available(const char *refname,
-                               const struct string_list *skip,
-                               struct ref_dir *dir)
+static int verify_refname_available(const char *refname,
+                                   const struct string_list *extras,
+                                   const struct string_list *skip,
+                                   struct ref_dir *dir,
+                                   struct strbuf *err)
 {
        const char *slash;
-       size_t len;
        int pos;
-       char *dirname;
+       struct strbuf dirname = STRBUF_INIT;
+       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; we are
-                * looking for a conflict with a leaf entry.
-                *
-                * If we find one, we still must make sure it is
-                * not in "skip".
+                * 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.
                 */
-               pos = search_ref_dir(dir, refname, slash - refname);
-               if (pos >= 0) {
-                       struct ref_entry *entry = dir->entries[pos];
-                       if (entry_matches(entry, skip))
-                               return 1;
-                       report_refname_conflict(entry, refname);
-                       return 0;
+               if (dir) {
+                       pos = search_ref_dir(dir, dirname.buf, dirname.len);
+                       if (pos >= 0 &&
+                           (!skip || !string_list_has_string(skip, dirname.buf))) {
+                               /*
+                                * We found a reference whose name is
+                                * a proper prefix of refname; e.g.,
+                                * "refs/foo", and is not in skip.
+                                */
+                               strbuf_addf(err, "'%s' exists; cannot create '%s'",
+                                           dirname.buf, refname);
+                               goto cleanup;
+                       }
                }
 
+               if (extras && string_list_has_string(extras, dirname.buf) &&
+                   (!skip || !string_list_has_string(skip, dirname.buf))) {
+                       strbuf_addf(err, "cannot process '%s' and '%s' at the same time",
+                                   refname, dirname.buf);
+                       goto cleanup;
+               }
 
                /*
                 * Otherwise, we can try to continue our search with
-                * the next component; if we come up empty, we know
-                * there is nothing under this whole prefix.
+                * the next component. So try to look up the
+                * directory, e.g., "refs/foo/". If we come up empty,
+                * we know there is nothing under this whole prefix,
+                * but even in that case we still have to continue the
+                * search for conflicts with extras.
                 */
-               pos = search_ref_dir(dir, refname, slash + 1 - refname);
-               if (pos < 0)
-                       return 1;
-
-               dir = get_ref_dir(dir->entries[pos]);
+               strbuf_addch(&dirname, '/');
+               if (dir) {
+                       pos = search_ref_dir(dir, dirname.buf, dirname.len);
+                       if (pos < 0) {
+                               /*
+                                * There was no directory "refs/foo/",
+                                * so there is nothing under this
+                                * whole prefix. So there is no need
+                                * to continue looking for conflicting
+                                * references. But we need to continue
+                                * looking for conflicting extras.
+                                */
+                               dir = NULL;
+                       } else {
+                               dir = get_ref_dir(dir->entries[pos]);
+                       }
+               }
        }
 
        /*
-        * We are at the leaf of our refname; we want to
-        * make sure there are no directories which match it.
+        * 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.
         */
-       len = strlen(refname);
-       dirname = xmallocz(len + 1);
-       sprintf(dirname, "%s/", refname);
-       pos = search_ref_dir(dir, dirname, len + 1);
-       free(dirname);
+       strbuf_addstr(&dirname, refname + dirname.len);
+       strbuf_addch(&dirname, '/');
+
+       if (dir) {
+               pos = search_ref_dir(dir, dirname.buf, dirname.len);
 
-       if (pos >= 0) {
+               if (pos >= 0) {
+                       /*
+                        * We found a directory named "$refname/"
+                        * (e.g., "refs/foo/bar/"). It is a problem
+                        * iff it contains any ref that is not in
+                        * "skip".
+                        */
+                       struct nonmatching_ref_data data;
+
+                       data.skip = skip;
+                       data.conflicting_refname = NULL;
+                       dir = get_ref_dir(dir->entries[pos]);
+                       sort_ref_dir(dir);
+                       if (do_for_each_entry_in_dir(dir, 0, nonmatching_ref_fn, &data)) {
+                               strbuf_addf(err, "'%s' exists; cannot create '%s'",
+                                           data.conflicting_refname, refname);
+                               goto cleanup;
+                       }
+               }
+       }
+
+       if (extras) {
                /*
-                * We found a directory named "refname". It is a
-                * problem iff it contains any ref that is not
-                * in "skip".
+                * Check for entries in extras that start with
+                * "$refname/". We do that by looking for the place
+                * where "$refname/" would be inserted in extras. If
+                * there is an entry at that position that starts with
+                * "$refname/" and is not in skip, then we have a
+                * conflict.
                 */
-               struct ref_entry *entry = dir->entries[pos];
-               struct ref_dir *dir = get_ref_dir(entry);
-               struct nonmatching_ref_data data;
+               for (pos = string_list_find_insert_index(extras, dirname.buf, 0);
+                    pos < extras->nr; pos++) {
+                       const char *extra_refname = extras->items[pos].string;
 
-               data.skip = skip;
-               sort_ref_dir(dir);
-               if (!do_for_each_entry_in_dir(dir, 0, nonmatching_ref_fn, &data))
-                       return 1;
+                       if (!starts_with(extra_refname, dirname.buf))
+                               break;
 
-               report_refname_conflict(data.found, refname);
-               return 0;
+                       if (!skip || !string_list_has_string(skip, extra_refname)) {
+                               strbuf_addf(err, "cannot process '%s' and '%s' at the same time",
+                                           refname, extra_refname);
+                               goto cleanup;
+                       }
+               }
        }
 
-       /*
-        * There is no point in searching for another leaf
-        * node which matches it; such an entry would be the
-        * ref we are looking for, not a conflict.
-        */
-       return 1;
+       /* No conflicts were found */
+       ret = 0;
+
+cleanup:
+       strbuf_release(&dirname);
+       return ret;
 }
 
 struct packed_ref_cache {
@@ -1151,6 +1241,8 @@ static void read_packed_refs(FILE *f, struct ref_dir *dir)
                        int flag = REF_ISPACKED;
 
                        if (check_refname_format(refname, REFNAME_ALLOW_ONELEVEL)) {
+                               if (!refname_is_safe(refname))
+                                       die("packed refname is dangerous: %s", refname);
                                hashclr(sha1);
                                flag |= REF_BAD_NAME | REF_ISBROKEN;
                        }
@@ -1166,7 +1258,7 @@ static void read_packed_refs(FILE *f, struct ref_dir *dir)
                    line.len == PEELED_LINE_LENGTH &&
                    line.buf[PEELED_LINE_LENGTH - 1] == '\n' &&
                    !get_sha1_hex(line.buf + 1, sha1)) {
-                       hashcpy(last->u.value.peeled, sha1);
+                       hashcpy(last->u.value.peeled.hash, sha1);
                        /*
                         * Regardless of what the file header said,
                         * we definitely know the value of *this*
@@ -1222,7 +1314,13 @@ static struct ref_dir *get_packed_refs(struct ref_cache *refs)
        return get_packed_ref_dir(get_packed_ref_cache(refs));
 }
 
-void add_packed_ref(const char *refname, const unsigned char *sha1)
+/*
+ * Add a reference to the in-memory packed reference cache.  This may
+ * only be called while the packed-refs file is locked (see
+ * lock_packed_refs()).  To actually write the packed-refs file, call
+ * commit_packed_refs().
+ */
+static void add_packed_ref(const char *refname, const unsigned char *sha1)
 {
        struct packed_ref_cache *packed_ref_cache =
                get_packed_ref_cache(&ref_cache);
@@ -1311,6 +1409,8 @@ static void read_loose_refs(const char *dirname, struct ref_dir *dir)
 
                        if (check_refname_format(refname.buf,
                                                 REFNAME_ALLOW_ONELEVEL)) {
+                               if (!refname_is_safe(refname.buf))
+                                       die("loose refname is dangerous: %s", refname.buf);
                                hashclr(sha1);
                                flag |= REF_BAD_NAME | REF_ISBROKEN;
                        }
@@ -1360,7 +1460,7 @@ static int resolve_gitlink_packed_ref(struct ref_cache *refs,
        if (ref == NULL)
                return -1;
 
-       hashcpy(sha1, ref->u.value.sha1);
+       hashcpy(sha1, ref->u.value.oid.hash);
        return 0;
 }
 
@@ -1370,7 +1470,7 @@ static int resolve_gitlink_ref_recursive(struct ref_cache *refs,
 {
        int fd, len;
        char buffer[128], *p;
-       char *path;
+       const char *path;
 
        if (recursion > MAXDEPTH || strlen(refname) > MAXREFLEN)
                return -1;
@@ -1447,7 +1547,7 @@ static int resolve_missing_loose_ref(const char *refname,
         */
        entry = get_packed_ref(refname);
        if (entry) {
-               hashcpy(sha1, entry->u.value.sha1);
+               hashcpy(sha1, entry->u.value.oid.hash);
                if (flags)
                        *flags |= REF_ISPACKED;
                return 0;
@@ -1463,7 +1563,11 @@ static int resolve_missing_loose_ref(const char *refname,
 }
 
 /* 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)
+static const char *resolve_ref_unsafe_1(const char *refname,
+                                       int resolve_flags,
+                                       unsigned char *sha1,
+                                       int *flags,
+                                       struct strbuf *sb_path)
 {
        int depth = MAXDEPTH;
        ssize_t len;
@@ -1494,7 +1598,7 @@ const char *resolve_ref_unsafe(const char *refname, int resolve_flags, unsigned
                bad_name = 1;
        }
        for (;;) {
-               char path[PATH_MAX];
+               const char *path;
                struct stat st;
                char *buf;
                int fd;
@@ -1504,7 +1608,9 @@ const char *resolve_ref_unsafe(const char *refname, int resolve_flags, unsigned
                        return NULL;
                }
 
-               git_snpath(path, sizeof(path), "%s", refname);
+               strbuf_reset(sb_path);
+               strbuf_git_path(sb_path, "%s", refname);
+               path = sb_path->buf;
 
                /*
                 * We might have to loop back here to avoid a race
@@ -1631,9 +1737,21 @@ const char *resolve_ref_unsafe(const char *refname, int resolve_flags, unsigned
        }
 }
 
-char *resolve_refdup(const char *ref, int resolve_flags, unsigned char *sha1, int *flags)
+const char *resolve_ref_unsafe(const char *refname, int resolve_flags,
+                              unsigned char *sha1, int *flags)
+{
+       struct strbuf sb_path = STRBUF_INIT;
+       const char *ret = resolve_ref_unsafe_1(refname, resolve_flags,
+                                              sha1, flags, &sb_path);
+       strbuf_release(&sb_path);
+       return ret;
+}
+
+char *resolve_refdup(const char *refname, int resolve_flags,
+                    unsigned char *sha1, int *flags)
 {
-       return xstrdup_or_null(resolve_ref_unsafe(ref, resolve_flags, sha1, flags));
+       return xstrdup_or_null(resolve_ref_unsafe(refname, resolve_flags,
+                                                 sha1, flags));
 }
 
 /* The argument to filter_refs */
@@ -1661,13 +1779,14 @@ int ref_exists(const char *refname)
        return !!resolve_ref_unsafe(refname, RESOLVE_REF_READING, sha1, NULL);
 }
 
-static int filter_refs(const char *refname, const unsigned char *sha1, int flags,
-                      void *data)
+static int filter_refs(const char *refname, const struct object_id *oid,
+                          int flags, void *data)
 {
        struct ref_filter *filter = (struct ref_filter *)data;
+
        if (wildmatch(filter->pattern, refname, 0, NULL))
                return 0;
-       return filter->fn(refname, sha1, flags, filter->cb_data);
+       return filter->fn(refname, oid, flags, filter->cb_data);
 }
 
 enum peel_status {
@@ -1741,9 +1860,9 @@ static enum peel_status peel_entry(struct ref_entry *entry, int repeel)
        if (entry->flag & REF_KNOWS_PEELED) {
                if (repeel) {
                        entry->flag &= ~REF_KNOWS_PEELED;
-                       hashclr(entry->u.value.peeled);
+                       oidclr(&entry->u.value.peeled);
                } else {
-                       return is_null_sha1(entry->u.value.peeled) ?
+                       return is_null_oid(&entry->u.value.peeled) ?
                                PEEL_NON_TAG : PEEL_PEELED;
                }
        }
@@ -1752,7 +1871,7 @@ static enum peel_status peel_entry(struct ref_entry *entry, int repeel)
        if (entry->flag & REF_ISSYMREF)
                return PEEL_IS_SYMREF;
 
-       status = peel_object(entry->u.value.sha1, entry->u.value.peeled);
+       status = peel_object(entry->u.value.oid.hash, entry->u.value.peeled.hash);
        if (status == PEEL_PEELED || status == PEEL_NON_TAG)
                entry->flag |= REF_KNOWS_PEELED;
        return status;
@@ -1767,7 +1886,7 @@ int peel_ref(const char *refname, unsigned char *sha1)
                            || !strcmp(current_ref->name, refname))) {
                if (peel_entry(current_ref, 0))
                        return -1;
-               hashcpy(sha1, current_ref->u.value.peeled);
+               hashcpy(sha1, current_ref->u.value.peeled.hash);
                return 0;
        }
 
@@ -1787,7 +1906,7 @@ int peel_ref(const char *refname, unsigned char *sha1)
                if (r) {
                        if (peel_entry(r, 0))
                                return -1;
-                       hashcpy(sha1, r->u.value.peeled);
+                       hashcpy(sha1, r->u.value.peeled.hash);
                        return 0;
                }
        }
@@ -1802,17 +1921,17 @@ struct warn_if_dangling_data {
        const char *msg_fmt;
 };
 
-static int warn_if_dangling_symref(const char *refname, const unsigned char *sha1,
+static int warn_if_dangling_symref(const char *refname, const struct object_id *oid,
                                   int flags, void *cb_data)
 {
        struct warn_if_dangling_data *d = cb_data;
        const char *resolves_to;
-       unsigned char junk[20];
+       struct object_id junk;
 
        if (!(flags & REF_ISSYMREF))
                return 0;
 
-       resolves_to = resolve_ref_unsafe(refname, 0, junk, NULL);
+       resolves_to = resolve_ref_unsafe(refname, 0, junk.hash, NULL);
        if (!resolves_to
            || (d->refname
                ? strcmp(resolves_to, d->refname)
@@ -1932,18 +2051,18 @@ static int do_for_each_ref(struct ref_cache *refs, const char *base,
 
 static int do_head_ref(const char *submodule, each_ref_fn fn, void *cb_data)
 {
-       unsigned char sha1[20];
+       struct object_id oid;
        int flag;
 
        if (submodule) {
-               if (resolve_gitlink_ref(submodule, "HEAD", sha1) == 0)
-                       return fn("HEAD", sha1, 0, cb_data);
+               if (resolve_gitlink_ref(submodule, "HEAD", oid.hash) == 0)
+                       return fn("HEAD", &oid, 0, cb_data);
 
                return 0;
        }
 
-       if (!read_ref_full("HEAD", RESOLVE_REF_READING, sha1, &flag))
-               return fn("HEAD", sha1, flag, cb_data);
+       if (!read_ref_full("HEAD", RESOLVE_REF_READING, oid.hash, &flag))
+               return fn("HEAD", &oid, flag, cb_data);
 
        return 0;
 }
@@ -2011,19 +2130,20 @@ int for_each_remote_ref_submodule(const char *submodule, each_ref_fn fn, void *c
 
 int for_each_replace_ref(each_ref_fn fn, void *cb_data)
 {
-       return do_for_each_ref(&ref_cache, "refs/replace/", fn, 13, 0, cb_data);
+       return do_for_each_ref(&ref_cache, git_replace_ref_base, fn,
+                              strlen(git_replace_ref_base), 0, cb_data);
 }
 
 int head_ref_namespaced(each_ref_fn fn, void *cb_data)
 {
        struct strbuf buf = STRBUF_INIT;
        int ret = 0;
-       unsigned char sha1[20];
+       struct object_id oid;
        int flag;
 
        strbuf_addf(&buf, "%sHEAD", get_git_namespace());
-       if (!read_ref_full(buf.buf, RESOLVE_REF_READING, sha1, &flag))
-               ret = fn(buf.buf, sha1, flag, cb_data);
+       if (!read_ref_full(buf.buf, RESOLVE_REF_READING, oid.hash, &flag))
+               ret = fn(buf.buf, &oid, flag, cb_data);
        strbuf_release(&buf);
 
        return ret;
@@ -2113,27 +2233,45 @@ int refname_match(const char *abbrev_name, const char *full_name)
        return 0;
 }
 
-/* This function should make sure errno is meaningful on error */
-static struct ref_lock *verify_lock(struct ref_lock *lock,
-       const unsigned char *old_sha1, int mustexist)
+static void unlock_ref(struct ref_lock *lock)
+{
+       /* Do not free lock->lk -- atexit() still looks at them */
+       if (lock->lk)
+               rollback_lock_file(lock->lk);
+       free(lock->ref_name);
+       free(lock->orig_ref_name);
+       free(lock);
+}
+
+/*
+ * Verify that the reference locked by lock has the value old_sha1.
+ * Fail if the reference doesn't exist and mustexist is set. Return 0
+ * on success. On error, write an error message to err, set errno, and
+ * return a negative value.
+ */
+static int verify_lock(struct ref_lock *lock,
+                      const unsigned char *old_sha1, int mustexist,
+                      struct strbuf *err)
 {
+       assert(err);
+
        if (read_ref_full(lock->ref_name,
                          mustexist ? RESOLVE_REF_READING : 0,
-                         lock->old_sha1, NULL)) {
+                         lock->old_oid.hash, NULL)) {
                int save_errno = errno;
-               error("Can't verify ref %s", lock->ref_name);
-               unlock_ref(lock);
+               strbuf_addf(err, "can't verify ref %s", lock->ref_name);
                errno = save_errno;
-               return NULL;
+               return -1;
        }
-       if (hashcmp(lock->old_sha1, old_sha1)) {
-               error("Ref %s is at %s but expected %s", lock->ref_name,
-                       sha1_to_hex(lock->old_sha1), sha1_to_hex(old_sha1));
-               unlock_ref(lock);
+       if (hashcmp(lock->old_oid.hash, old_sha1)) {
+               strbuf_addf(err, "ref %s is at %s but expected %s",
+                           lock->ref_name,
+                           sha1_to_hex(lock->old_oid.hash),
+                           sha1_to_hex(old_sha1));
                errno = EBUSY;
-               return NULL;
+               return -1;
        }
-       return lock;
+       return 0;
 }
 
 static int remove_empty_directories(const char *file)
@@ -2249,21 +2387,23 @@ int dwim_log(const char *str, int len, unsigned char *sha1, char **log)
  */
 static struct ref_lock *lock_ref_sha1_basic(const char *refname,
                                            const unsigned char *old_sha1,
+                                           const struct string_list *extras,
                                            const struct string_list *skip,
-                                           int flags, int *type_p)
+                                           unsigned int flags, int *type_p,
+                                           struct strbuf *err)
 {
-       char *ref_file;
+       const char *ref_file;
        const char *orig_refname = refname;
        struct ref_lock *lock;
        int last_errno = 0;
        int type, lflags;
        int mustexist = (old_sha1 && !is_null_sha1(old_sha1));
        int resolve_flags = 0;
-       int missing = 0;
        int attempts_remaining = 3;
 
+       assert(err);
+
        lock = xcalloc(1, sizeof(struct ref_lock));
-       lock->lock_fd = -1;
 
        if (mustexist)
                resolve_flags |= RESOLVE_REF_READING;
@@ -2274,7 +2414,7 @@ static struct ref_lock *lock_ref_sha1_basic(const char *refname,
        }
 
        refname = resolve_ref_unsafe(refname, resolve_flags,
-                                    lock->old_sha1, &type);
+                                    lock->old_oid.hash, &type);
        if (!refname && errno == EISDIR) {
                /* we are trying to lock foo but we used to
                 * have foo/bar which now does not exist;
@@ -2284,28 +2424,38 @@ static struct ref_lock *lock_ref_sha1_basic(const char *refname,
                ref_file = git_path("%s", orig_refname);
                if (remove_empty_directories(ref_file)) {
                        last_errno = errno;
-                       error("there are still refs under '%s'", orig_refname);
+
+                       if (!verify_refname_available(orig_refname, extras, skip,
+                                                     get_loose_refs(&ref_cache), err))
+                               strbuf_addf(err, "there are still refs under '%s'",
+                                           orig_refname);
+
                        goto error_return;
                }
                refname = resolve_ref_unsafe(orig_refname, resolve_flags,
-                                            lock->old_sha1, &type);
+                                            lock->old_oid.hash, &type);
        }
        if (type_p)
            *type_p = type;
        if (!refname) {
                last_errno = errno;
-               error("unable to resolve reference %s: %s",
-                       orig_refname, strerror(errno));
+               if (last_errno != ENOTDIR ||
+                   !verify_refname_available(orig_refname, extras, skip,
+                                             get_loose_refs(&ref_cache), err))
+                       strbuf_addf(err, "unable to resolve reference %s: %s",
+                                   orig_refname, strerror(last_errno));
+
                goto error_return;
        }
-       missing = is_null_sha1(lock->old_sha1);
-       /* When the ref did not exist and we are creating it,
-        * make sure there is no existing ref that is packed
-        * whose name begins with our refname, nor a ref whose
-        * name is a proper prefix of our refname.
+       /*
+        * If the ref did not exist and we are creating it, make sure
+        * there is no existing packed ref whose name begins with our
+        * refname, nor a packed ref whose name is a proper prefix of
+        * our refname.
         */
-       if (missing &&
-            !is_refname_available(refname, skip, get_packed_refs(&ref_cache))) {
+       if (is_null_oid(&lock->old_oid) &&
+           verify_refname_available(refname, extras, skip,
+                                    get_packed_refs(&ref_cache), err)) {
                last_errno = ENOTDIR;
                goto error_return;
        }
@@ -2320,13 +2470,9 @@ static struct ref_lock *lock_ref_sha1_basic(const char *refname,
        lock->ref_name = xstrdup(refname);
        lock->orig_ref_name = xstrdup(orig_refname);
        ref_file = git_path("%s", refname);
-       if (missing)
-               lock->force_write = 1;
-       if ((flags & REF_NODEREF) && (type & REF_ISSYMREF))
-               lock->force_write = 1;
 
  retry:
-       switch (safe_create_leading_directories(ref_file)) {
+       switch (safe_create_leading_directories_const(ref_file)) {
        case SCLD_OK:
                break; /* success */
        case SCLD_VANISHED:
@@ -2335,12 +2481,11 @@ static struct ref_lock *lock_ref_sha1_basic(const char *refname,
                /* fall through */
        default:
                last_errno = errno;
-               error("unable to create directory for %s", ref_file);
+               strbuf_addf(err, "unable to create directory for %s", ref_file);
                goto error_return;
        }
 
-       lock->lock_fd = hold_lock_file_for_update(lock->lk, ref_file, lflags);
-       if (lock->lock_fd < 0) {
+       if (hold_lock_file_for_update(lock->lk, ref_file, lflags) < 0) {
                last_errno = errno;
                if (errno == ENOENT && --attempts_remaining > 0)
                        /*
@@ -2350,14 +2495,15 @@ static struct ref_lock *lock_ref_sha1_basic(const char *refname,
                         */
                        goto retry;
                else {
-                       struct strbuf err = STRBUF_INIT;
-                       unable_to_lock_message(ref_file, errno, &err);
-                       error("%s", err.buf);
-                       strbuf_release(&err);
+                       unable_to_lock_message(ref_file, errno, err);
                        goto error_return;
                }
        }
-       return old_sha1 ? verify_lock(lock, old_sha1, mustexist) : lock;
+       if (old_sha1 && verify_lock(lock, old_sha1, mustexist, err)) {
+               last_errno = errno;
+               goto error_return;
+       }
+       return lock;
 
  error_return:
        unlock_ref(lock);
@@ -2365,13 +2511,6 @@ static struct ref_lock *lock_ref_sha1_basic(const char *refname,
        return NULL;
 }
 
-struct ref_lock *lock_any_ref_for_update(const char *refname,
-                                        const unsigned char *old_sha1,
-                                        int flags, int *type_p)
-{
-       return lock_ref_sha1_basic(refname, old_sha1, NULL, flags, type_p);
-}
-
 /*
  * Write an entry to the packed-refs file for the specified refname.
  * If peeled is non-NULL, write it as the entry's peeled value.
@@ -2394,18 +2533,32 @@ static int write_packed_entry_fn(struct ref_entry *entry, void *cb_data)
        if (peel_status != PEEL_PEELED && peel_status != PEEL_NON_TAG)
                error("internal error: %s is not a valid packed reference!",
                      entry->name);
-       write_packed_entry(cb_data, entry->name, entry->u.value.sha1,
+       write_packed_entry(cb_data, entry->name, entry->u.value.oid.hash,
                           peel_status == PEEL_PEELED ?
-                          entry->u.value.peeled : NULL);
+                          entry->u.value.peeled.hash : NULL);
        return 0;
 }
 
-/* This should return a meaningful errno on failure */
-int lock_packed_refs(int flags)
+/*
+ * Lock the packed-refs file for writing. Flags is passed to
+ * hold_lock_file_for_update(). Return 0 on success. On errors, set
+ * errno appropriately and return a nonzero value.
+ */
+static int lock_packed_refs(int flags)
 {
+       static int timeout_configured = 0;
+       static int timeout_value = 1000;
+
        struct packed_ref_cache *packed_ref_cache;
 
-       if (hold_lock_file_for_update(&packlock, git_path("packed-refs"), flags) < 0)
+       if (!timeout_configured) {
+               git_config_get_int("core.packedrefstimeout", &timeout_value);
+               timeout_configured = 1;
+       }
+
+       if (hold_lock_file_for_update_timeout(
+                           &packlock, git_path("packed-refs"),
+                           flags, timeout_value) < 0)
                return -1;
        /*
         * Get the current packed-refs while holding the lock.  If the
@@ -2421,10 +2574,12 @@ int lock_packed_refs(int flags)
 }
 
 /*
- * Commit the packed refs changes.
- * On error we must make sure that errno contains a meaningful value.
+ * Write the current version of the packed refs cache from memory to
+ * disk. The packed-refs file must already be locked for writing (see
+ * lock_packed_refs()). Return zero on success. On errors, set errno
+ * and return a nonzero value
  */
-int commit_packed_refs(void)
+static int commit_packed_refs(void)
 {
        struct packed_ref_cache *packed_ref_cache =
                get_packed_ref_cache(&ref_cache);
@@ -2453,7 +2608,12 @@ int commit_packed_refs(void)
        return error;
 }
 
-void rollback_packed_refs(void)
+/*
+ * Rollback the lockfile for the packed-refs file, and discard the
+ * in-memory packed reference cache.  (The packed-refs file will be
+ * read anew if it is needed again after this function is called.)
+ */
+static void rollback_packed_refs(void)
 {
        struct packed_ref_cache *packed_ref_cache =
                get_packed_ref_cache(&ref_cache);
@@ -2503,24 +2663,24 @@ static int pack_if_possible_fn(struct ref_entry *entry, void *cb_data)
        peel_status = peel_entry(entry, 1);
        if (peel_status != PEEL_PEELED && peel_status != PEEL_NON_TAG)
                die("internal error peeling reference %s (%s)",
-                   entry->name, sha1_to_hex(entry->u.value.sha1));
+                   entry->name, oid_to_hex(&entry->u.value.oid));
        packed_entry = find_ref(cb->packed_refs, entry->name);
        if (packed_entry) {
                /* Overwrite existing packed entry with info from loose entry */
                packed_entry->flag = REF_ISPACKED | REF_KNOWS_PEELED;
-               hashcpy(packed_entry->u.value.sha1, entry->u.value.sha1);
+               oidcpy(&packed_entry->u.value.oid, &entry->u.value.oid);
        } else {
-               packed_entry = create_ref_entry(entry->name, entry->u.value.sha1,
+               packed_entry = create_ref_entry(entry->name, entry->u.value.oid.hash,
                                                REF_ISPACKED | REF_KNOWS_PEELED, 0);
                add_ref(cb->packed_refs, packed_entry);
        }
-       hashcpy(packed_entry->u.value.peeled, entry->u.value.peeled);
+       oidcpy(&packed_entry->u.value.peeled, &entry->u.value.peeled);
 
        /* Schedule the loose reference for pruning if requested. */
        if ((cb->flags & PACK_REFS_PRUNE)) {
                int namelen = strlen(entry->name) + 1;
                struct ref_to_prune *n = xcalloc(1, sizeof(*n) + namelen);
-               hashcpy(n->sha1, entry->u.value.sha1);
+               hashcpy(n->sha1, entry->u.value.oid.hash);
                strcpy(n->name, entry->name);
                n->next = cb->ref_to_prune;
                cb->ref_to_prune = n;
@@ -2571,7 +2731,7 @@ static void prune_ref(struct ref_to_prune *r)
        transaction = ref_transaction_begin(&err);
        if (!transaction ||
            ref_transaction_delete(transaction, r->name, r->sha1,
-                                  REF_ISPRUNING, 1, NULL, &err) ||
+                                  REF_ISPRUNING, NULL, &err) ||
            ref_transaction_commit(transaction, &err)) {
                ref_transaction_free(transaction);
                error("%s", err.buf);
@@ -2611,7 +2771,14 @@ int pack_refs(unsigned int flags)
        return 0;
 }
 
-int repack_without_refs(struct string_list *refnames, struct strbuf *err)
+/*
+ * Rewrite the packed-refs file, omitting any refs listed in
+ * 'refnames'. On error, leave packed-refs unchanged, write an error
+ * message to 'err', and return a nonzero value.
+ *
+ * The refs in 'refnames' needn't be sorted. `err` must not be NULL.
+ */
+static int repack_without_refs(struct string_list *refnames, struct strbuf *err)
 {
        struct ref_dir *packed;
        struct string_list_item *refname;
@@ -2676,15 +2843,16 @@ static int delete_ref_loose(struct ref_lock *lock, int flag, struct strbuf *err)
        return 0;
 }
 
-int delete_ref(const char *refname, const unsigned char *sha1, int delopt)
+int delete_ref(const char *refname, const unsigned char *old_sha1,
+              unsigned int flags)
 {
        struct ref_transaction *transaction;
        struct strbuf err = STRBUF_INIT;
 
        transaction = ref_transaction_begin(&err);
        if (!transaction ||
-           ref_transaction_delete(transaction, refname, sha1, delopt,
-                                  sha1 && !is_null_sha1(sha1), NULL, &err) ||
+           ref_transaction_delete(transaction, refname, old_sha1,
+                                  flags, NULL, &err) ||
            ref_transaction_commit(transaction, &err)) {
                error("%s", err.buf);
                ref_transaction_free(transaction);
@@ -2696,6 +2864,44 @@ int delete_ref(const char *refname, const unsigned char *sha1, int delopt)
        return 0;
 }
 
+int delete_refs(struct string_list *refnames)
+{
+       struct strbuf err = STRBUF_INIT;
+       int i, result = 0;
+
+       if (!refnames->nr)
+               return 0;
+
+       result = repack_without_refs(refnames, &err);
+       if (result) {
+               /*
+                * If we failed to rewrite the packed-refs file, then
+                * it is unsafe to try to remove loose refs, because
+                * doing so might expose an obsolete packed value for
+                * a reference that might even point at an object that
+                * has been garbage collected.
+                */
+               if (refnames->nr == 1)
+                       error(_("could not delete reference %s: %s"),
+                             refnames->items[0].string, err.buf);
+               else
+                       error(_("could not delete references: %s"), err.buf);
+
+               goto out;
+       }
+
+       for (i = 0; i < refnames->nr; i++) {
+               const char *refname = refnames->items[i].string;
+
+               if (delete_ref(refname, NULL, 0))
+                       result |= error(_("could not remove reference %s"), refname);
+       }
+
+out:
+       strbuf_release(&err);
+       return result;
+}
+
 /*
  * People using contrib's git-new-workdir have .git/logs/refs ->
  * /some/other/path/.git/logs/refs, and that may live on another device.
@@ -2710,7 +2916,7 @@ static int rename_tmp_log(const char *newrefname)
        int attempts_remaining = 4;
 
  retry:
-       switch (safe_create_leading_directories(git_path("logs/%s", newrefname))) {
+       switch (safe_create_leading_directories_const(git_path("logs/%s", newrefname))) {
        case SCLD_OK:
                break; /* success */
        case SCLD_VANISHED:
@@ -2753,17 +2959,25 @@ static int rename_tmp_log(const char *newrefname)
 static int rename_ref_available(const char *oldname, const char *newname)
 {
        struct string_list skip = STRING_LIST_INIT_NODUP;
+       struct strbuf err = STRBUF_INIT;
        int ret;
 
        string_list_insert(&skip, oldname);
-       ret = is_refname_available(newname, &skip, get_packed_refs(&ref_cache))
-           && is_refname_available(newname, &skip, get_loose_refs(&ref_cache));
+       ret = !verify_refname_available(newname, NULL, &skip,
+                                       get_packed_refs(&ref_cache), &err)
+               && !verify_refname_available(newname, NULL, &skip,
+                                            get_loose_refs(&ref_cache), &err);
+       if (!ret)
+               error("%s", err.buf);
+
        string_list_clear(&skip, 0);
+       strbuf_release(&err);
        return ret;
 }
 
-static int write_ref_sha1(struct ref_lock *lock, const unsigned char *sha1,
-                         const char *logmsg);
+static int write_ref_to_lockfile(struct ref_lock *lock, const unsigned char *sha1);
+static int commit_ref_update(struct ref_lock *lock,
+                            const unsigned char *sha1, const char *logmsg);
 
 int rename_ref(const char *oldrefname, const char *newrefname, const char *logmsg)
 {
@@ -2773,6 +2987,7 @@ int rename_ref(const char *oldrefname, const char *newrefname, const char *logms
        struct stat loginfo;
        int log = !lstat(git_path("logs/%s", oldrefname), &loginfo);
        const char *symref = NULL;
+       struct strbuf err = STRBUF_INIT;
 
        if (log && S_ISLNK(loginfo.st_mode))
                return error("reflog for %s is a symlink", oldrefname);
@@ -2815,14 +3030,16 @@ int rename_ref(const char *oldrefname, const char *newrefname, const char *logms
 
        logmoved = log;
 
-       lock = lock_ref_sha1_basic(newrefname, NULL, NULL, 0, NULL);
+       lock = lock_ref_sha1_basic(newrefname, NULL, NULL, NULL, 0, NULL, &err);
        if (!lock) {
-               error("unable to lock %s for update", newrefname);
+               error("unable to rename '%s' to '%s': %s", oldrefname, newrefname, err.buf);
+               strbuf_release(&err);
                goto rollback;
        }
-       lock->force_write = 1;
-       hashcpy(lock->old_sha1, orig_sha1);
-       if (write_ref_sha1(lock, orig_sha1, logmsg)) {
+       hashcpy(lock->old_oid.hash, orig_sha1);
+
+       if (write_ref_to_lockfile(lock, orig_sha1) ||
+           commit_ref_update(lock, orig_sha1, logmsg)) {
                error("unable to write current sha1 into %s", newrefname);
                goto rollback;
        }
@@ -2830,16 +3047,17 @@ int rename_ref(const char *oldrefname, const char *newrefname, const char *logms
        return 0;
 
  rollback:
-       lock = lock_ref_sha1_basic(oldrefname, NULL, NULL, 0, NULL);
+       lock = lock_ref_sha1_basic(oldrefname, NULL, NULL, NULL, 0, NULL, &err);
        if (!lock) {
-               error("unable to lock %s for rollback", oldrefname);
+               error("unable to lock %s for rollback: %s", oldrefname, err.buf);
+               strbuf_release(&err);
                goto rollbacklog;
        }
 
-       lock->force_write = 1;
        flag = log_all_ref_updates;
        log_all_ref_updates = 0;
-       if (write_ref_sha1(lock, orig_sha1, NULL))
+       if (write_ref_to_lockfile(lock, orig_sha1) ||
+           commit_ref_update(lock, orig_sha1, NULL))
                error("unable to write current sha1 into %s", oldrefname);
        log_all_ref_updates = flag;
 
@@ -2855,32 +3073,20 @@ int rename_ref(const char *oldrefname, const char *newrefname, const char *logms
        return 1;
 }
 
-int close_ref(struct ref_lock *lock)
+static int close_ref(struct ref_lock *lock)
 {
        if (close_lock_file(lock->lk))
                return -1;
-       lock->lock_fd = -1;
        return 0;
 }
 
-int commit_ref(struct ref_lock *lock)
+static int commit_ref(struct ref_lock *lock)
 {
        if (commit_lock_file(lock->lk))
                return -1;
-       lock->lock_fd = -1;
        return 0;
 }
 
-void unlock_ref(struct ref_lock *lock)
-{
-       /* Do not free lock->lk -- atexit() still looks at them */
-       if (lock->lk)
-               rollback_lock_file(lock->lk);
-       free(lock->ref_name);
-       free(lock->orig_ref_name);
-       free(lock);
-}
-
 /*
  * copy the reflog message msg to buf, which has been allocated sufficiently
  * large, while cleaning up the whitespaces.  Especially, convert LF to space,
@@ -2908,11 +3114,15 @@ static int copy_msg(char *buf, const char *msg)
 }
 
 /* This function must set a meaningful errno on failure */
-int log_ref_setup(const char *refname, char *logfile, int bufsize)
+int log_ref_setup(const char *refname, struct strbuf *sb_logfile)
 {
        int logfd, oflags = O_APPEND | O_WRONLY;
+       char *logfile;
 
-       git_snpath(logfile, bufsize, "logs/%s", refname);
+       strbuf_git_path(sb_logfile, "logs/%s", refname);
+       logfile = sb_logfile->buf;
+       /* make sure the rest of the function can't change "logfile" */
+       sb_logfile = NULL;
        if (log_all_ref_updates &&
            (starts_with(refname, "refs/heads/") ||
             starts_with(refname, "refs/remotes/") ||
@@ -2957,28 +3167,15 @@ int log_ref_setup(const char *refname, char *logfile, int bufsize)
        return 0;
 }
 
-static int log_ref_write(const char *refname, const unsigned char *old_sha1,
-                        const unsigned char *new_sha1, const char *msg)
+static int log_ref_write_fd(int fd, const unsigned char *old_sha1,
+                           const unsigned char *new_sha1,
+                           const char *committer, const char *msg)
 {
-       int logfd, result, written, oflags = O_APPEND | O_WRONLY;
+       int msglen, written;
        unsigned maxlen, len;
-       int msglen;
-       char log_file[PATH_MAX];
        char *logrec;
-       const char *committer;
-
-       if (log_all_ref_updates < 0)
-               log_all_ref_updates = !is_bare_repository();
-
-       result = log_ref_setup(refname, log_file, sizeof(log_file));
-       if (result)
-               return result;
 
-       logfd = open(log_file, oflags);
-       if (logfd < 0)
-               return 0;
        msglen = msg ? strlen(msg) : 0;
-       committer = git_committer_info(0);
        maxlen = strlen(committer) + msglen + 100;
        logrec = xmalloc(maxlen);
        len = sprintf(logrec, "%s %s %s\n",
@@ -2987,9 +3184,38 @@ static int log_ref_write(const char *refname, const unsigned char *old_sha1,
                      committer);
        if (msglen)
                len += copy_msg(logrec + len - 1, msg) - 1;
-       written = len <= maxlen ? write_in_full(logfd, logrec, len) : -1;
+
+       written = len <= maxlen ? write_in_full(fd, logrec, len) : -1;
        free(logrec);
-       if (written != len) {
+       if (written != len)
+               return -1;
+
+       return 0;
+}
+
+static int log_ref_write_1(const char *refname, const unsigned char *old_sha1,
+                          const unsigned char *new_sha1, const char *msg,
+                          struct strbuf *sb_log_file)
+{
+       int logfd, result, oflags = O_APPEND | O_WRONLY;
+       char *log_file;
+
+       if (log_all_ref_updates < 0)
+               log_all_ref_updates = !is_bare_repository();
+
+       result = log_ref_setup(refname, sb_log_file);
+       if (result)
+               return result;
+       log_file = sb_log_file->buf;
+       /* make sure the rest of the function can't change "log_file" */
+       sb_log_file = NULL;
+
+       logfd = open(log_file, oflags);
+       if (logfd < 0)
+               return 0;
+       result = log_ref_write_fd(logfd, old_sha1, new_sha1,
+                                 git_committer_info(0), msg);
+       if (result) {
                int save_errno = errno;
                close(logfd);
                error("Unable to append to %s", log_file);
@@ -3005,29 +3231,30 @@ static int log_ref_write(const char *refname, const unsigned char *old_sha1,
        return 0;
 }
 
+static int log_ref_write(const char *refname, const unsigned char *old_sha1,
+                        const unsigned char *new_sha1, const char *msg)
+{
+       struct strbuf sb = STRBUF_INIT;
+       int ret = log_ref_write_1(refname, old_sha1, new_sha1, msg, &sb);
+       strbuf_release(&sb);
+       return ret;
+}
+
 int is_branch(const char *refname)
 {
        return !strcmp(refname, "HEAD") || starts_with(refname, "refs/heads/");
 }
 
 /*
- * Write sha1 into the ref specified by the lock. Make sure that errno
- * is sane on error.
+ * Write sha1 into the open lockfile, then close the lockfile. On
+ * errors, rollback the lockfile and set errno to reflect the problem.
  */
-static int write_ref_sha1(struct ref_lock *lock,
-       const unsigned char *sha1, const char *logmsg)
+static int write_ref_to_lockfile(struct ref_lock *lock,
+                                const unsigned char *sha1)
 {
        static char term = '\n';
        struct object *o;
 
-       if (!lock) {
-               errno = EINVAL;
-               return -1;
-       }
-       if (!lock->force_write && !hashcmp(lock->old_sha1, sha1)) {
-               unlock_ref(lock);
-               return 0;
-       }
        o = parse_object(sha1);
        if (!o) {
                error("Trying to write ref %s with nonexistent object %s",
@@ -3043,8 +3270,8 @@ static int write_ref_sha1(struct ref_lock *lock,
                errno = EINVAL;
                return -1;
        }
-       if (write_in_full(lock->lock_fd, sha1_to_hex(sha1), 40) != 40 ||
-           write_in_full(lock->lock_fd, &term, 1) != 1 ||
+       if (write_in_full(lock->lk->fd, sha1_to_hex(sha1), 40) != 40 ||
+           write_in_full(lock->lk->fd, &term, 1) != 1 ||
            close_ref(lock) < 0) {
                int save_errno = errno;
                error("Couldn't write %s", lock->lk->filename.buf);
@@ -3052,10 +3279,21 @@ static int write_ref_sha1(struct ref_lock *lock,
                errno = save_errno;
                return -1;
        }
+       return 0;
+}
+
+/*
+ * Commit a change to a loose reference that has already been written
+ * to the loose reference lockfile. Also update the reflogs if
+ * necessary, using the specified lockmsg (which can be NULL).
+ */
+static int commit_ref_update(struct ref_lock *lock,
+                            const unsigned char *sha1, const char *logmsg)
+{
        clear_loose_ref_cache(&ref_cache);
-       if (log_ref_write(lock->ref_name, lock->old_sha1, sha1, logmsg) < 0 ||
+       if (log_ref_write(lock->ref_name, lock->old_oid.hash, sha1, logmsg) < 0 ||
            (strcmp(lock->ref_name, lock->orig_ref_name) &&
-            log_ref_write(lock->orig_ref_name, lock->old_sha1, sha1, logmsg) < 0)) {
+            log_ref_write(lock->orig_ref_name, lock->old_oid.hash, sha1, logmsg) < 0)) {
                unlock_ref(lock);
                return -1;
        }
@@ -3079,7 +3317,7 @@ static int write_ref_sha1(struct ref_lock *lock,
                                              head_sha1, &head_flag);
                if (head_ref && (head_flag & REF_ISSYMREF) &&
                    !strcmp(head_ref, lock->ref_name))
-                       log_ref_write("HEAD", lock->old_sha1, sha1, logmsg);
+                       log_ref_write("HEAD", lock->old_oid.hash, sha1, logmsg);
        }
        if (commit_ref(lock)) {
                error("Couldn't set %s", lock->ref_name);
@@ -3198,14 +3436,14 @@ static int read_ref_at_ent(unsigned char *osha1, unsigned char *nsha1,
                        hashcpy(cb->sha1, nsha1);
                        if (hashcmp(cb->osha1, nsha1))
                                warning("Log for ref %s has gap after %s.",
-                                       cb->refname, show_date(cb->date, cb->tz, DATE_RFC2822));
+                                       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))
                        warning("Log for ref %s unexpectedly ended on %s.",
                                cb->refname, show_date(cb->date, cb->tz,
-                                                  DATE_RFC2822));
+                                                      DATE_MODE(RFC2822)));
                hashcpy(cb->osha1, osha1);
                hashcpy(cb->nsha1, nsha1);
                cb->found_it = 1;
@@ -3471,11 +3709,12 @@ static int do_for_each_reflog(struct strbuf *name, each_ref_fn fn, void *cb_data
                                strbuf_addch(name, '/');
                                retval = do_for_each_reflog(name, fn, cb_data);
                        } else {
-                               unsigned char sha1[20];
-                               if (read_ref_full(name->buf, 0, sha1, NULL))
+                               struct object_id oid;
+
+                               if (read_ref_full(name->buf, 0, oid.hash, NULL))
                                        retval = error("bad ref for %s", name->buf);
                                else
-                                       retval = fn(name->buf, sha1, 0, cb_data);
+                                       retval = fn(name->buf, &oid, 0, cb_data);
                        }
                        if (retval)
                                break;
@@ -3497,16 +3736,27 @@ int for_each_reflog(each_ref_fn fn, void *cb_data)
 }
 
 /**
- * Information needed for a single ref update.  Set new_sha1 to the
- * new value or to zero to delete the ref.  To check the old value
- * while locking the ref, set have_old to 1 and set old_sha1 to the
- * value or to zero to ensure the ref does not exist before update.
+ * Information needed for a single ref update. Set new_sha1 to the new
+ * value or to null_sha1 to delete the ref. To check the old value
+ * while the ref is locked, set (flags & REF_HAVE_OLD) and set
+ * old_sha1 to the old value, or to null_sha1 to ensure the ref does
+ * not exist before update.
  */
 struct ref_update {
+       /*
+        * If (flags & REF_HAVE_NEW), set the reference to this value:
+        */
        unsigned char new_sha1[20];
+       /*
+        * If (flags & REF_HAVE_OLD), check that the reference
+        * previously had this value:
+        */
        unsigned char old_sha1[20];
-       int flags; /* REF_NODEREF? */
-       int have_old; /* 1 if old_sha1 is valid, 0 otherwise */
+       /*
+        * One or more of REF_HAVE_NEW, REF_HAVE_OLD, REF_NODEREF,
+        * REF_DELETING, and REF_ISPRUNING:
+        */
+       unsigned int flags;
        struct ref_lock *lock;
        int type;
        char *msg;
@@ -3578,7 +3828,7 @@ int ref_transaction_update(struct ref_transaction *transaction,
                           const char *refname,
                           const unsigned char *new_sha1,
                           const unsigned char *old_sha1,
-                          int flags, int have_old, const char *msg,
+                          unsigned int flags, const char *msg,
                           struct strbuf *err)
 {
        struct ref_update *update;
@@ -3588,10 +3838,7 @@ int ref_transaction_update(struct ref_transaction *transaction,
        if (transaction->state != REF_TRANSACTION_OPEN)
                die("BUG: update called for transaction that is not open");
 
-       if (have_old && !old_sha1)
-               die("BUG: have_old is true but old_sha1 is NULL");
-
-       if (!is_null_sha1(new_sha1) &&
+       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",
                            refname);
@@ -3599,11 +3846,15 @@ int ref_transaction_update(struct ref_transaction *transaction,
        }
 
        update = add_update(transaction, refname);
-       hashcpy(update->new_sha1, new_sha1);
-       update->flags = flags;
-       update->have_old = have_old;
-       if (have_old)
+       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);
        return 0;
@@ -3612,75 +3863,52 @@ int ref_transaction_update(struct ref_transaction *transaction,
 int ref_transaction_create(struct ref_transaction *transaction,
                           const char *refname,
                           const unsigned char *new_sha1,
-                          int flags, const char *msg,
+                          unsigned int flags, const char *msg,
                           struct strbuf *err)
 {
-       struct ref_update *update;
-
-       assert(err);
-
-       if (transaction->state != REF_TRANSACTION_OPEN)
-               die("BUG: create called for transaction that is not open");
-
        if (!new_sha1 || is_null_sha1(new_sha1))
-               die("BUG: create ref with null new_sha1");
-
-       if (check_refname_format(refname, REFNAME_ALLOW_ONELEVEL)) {
-               strbuf_addf(err, "refusing to create ref with bad name %s",
-                           refname);
-               return -1;
-       }
-
-       update = add_update(transaction, refname);
-
-       hashcpy(update->new_sha1, new_sha1);
-       hashclr(update->old_sha1);
-       update->flags = flags;
-       update->have_old = 1;
-       if (msg)
-               update->msg = xstrdup(msg);
-       return 0;
+               die("BUG: create called without valid new_sha1");
+       return ref_transaction_update(transaction, refname, new_sha1,
+                                     null_sha1, flags, msg, err);
 }
 
 int ref_transaction_delete(struct ref_transaction *transaction,
                           const char *refname,
                           const unsigned char *old_sha1,
-                          int flags, int have_old, const char *msg,
+                          unsigned int flags, const char *msg,
                           struct strbuf *err)
 {
-       struct ref_update *update;
-
-       assert(err);
-
-       if (transaction->state != REF_TRANSACTION_OPEN)
-               die("BUG: delete called for transaction that is not open");
-
-       if (have_old && !old_sha1)
-               die("BUG: have_old is true but old_sha1 is NULL");
+       if (old_sha1 && is_null_sha1(old_sha1))
+               die("BUG: delete called with old_sha1 set to zeros");
+       return ref_transaction_update(transaction, refname,
+                                     null_sha1, old_sha1,
+                                     flags, msg, err);
+}
 
-       update = add_update(transaction, refname);
-       update->flags = flags;
-       update->have_old = have_old;
-       if (have_old) {
-               assert(!is_null_sha1(old_sha1));
-               hashcpy(update->old_sha1, old_sha1);
-       }
-       if (msg)
-               update->msg = xstrdup(msg);
-       return 0;
+int ref_transaction_verify(struct ref_transaction *transaction,
+                          const char *refname,
+                          const unsigned char *old_sha1,
+                          unsigned int flags,
+                          struct strbuf *err)
+{
+       if (!old_sha1)
+               die("BUG: verify called with old_sha1 set to NULL");
+       return ref_transaction_update(transaction, refname,
+                                     NULL, old_sha1,
+                                     flags, NULL, err);
 }
 
-int update_ref(const char *action, const char *refname,
-              const unsigned char *sha1, const unsigned char *oldval,
-              int flags, enum action_on_err onerr)
+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)
 {
        struct ref_transaction *t;
        struct strbuf err = STRBUF_INIT;
 
        t = ref_transaction_begin(&err);
        if (!t ||
-           ref_transaction_update(t, refname, sha1, oldval, flags,
-                                  !!oldval, action, &err) ||
+           ref_transaction_update(t, refname, new_sha1, old_sha1,
+                                  flags, msg, &err) ||
            ref_transaction_commit(t, &err)) {
                const char *str = "update_ref failed for ref '%s': %s";
 
@@ -3703,25 +3931,18 @@ int update_ref(const char *action, const char *refname,
        return 0;
 }
 
-static int ref_update_compare(const void *r1, const void *r2)
-{
-       const struct ref_update * const *u1 = r1;
-       const struct ref_update * const *u2 = r2;
-       return strcmp((*u1)->refname, (*u2)->refname);
-}
-
-static int ref_update_reject_duplicates(struct ref_update **updates, int n,
+static int ref_update_reject_duplicates(struct string_list *refnames,
                                        struct strbuf *err)
 {
-       int i;
+       int i, n = refnames->nr;
 
        assert(err);
 
        for (i = 1; i < n; i++)
-               if (!strcmp(updates[i - 1]->refname, updates[i]->refname)) {
+               if (!strcmp(refnames->items[i - 1].string, refnames->items[i].string)) {
                        strbuf_addf(err,
                                    "Multiple updates for ref '%s' not allowed.",
-                                   updates[i]->refname);
+                                   refnames->items[i].string);
                        return 1;
                }
        return 0;
@@ -3735,6 +3956,7 @@ int ref_transaction_commit(struct ref_transaction *transaction,
        struct ref_update **updates = transaction->updates;
        struct string_list refs_to_delete = STRING_LIST_INIT_NODUP;
        struct string_list_item *ref_to_delete;
+       struct string_list affected_refnames = STRING_LIST_INIT_NODUP;
 
        assert(err);
 
@@ -3746,51 +3968,103 @@ int ref_transaction_commit(struct ref_transaction *transaction,
                return 0;
        }
 
-       /* Copy, sort, and reject duplicate refs */
-       qsort(updates, n, sizeof(*updates), ref_update_compare);
-       if (ref_update_reject_duplicates(updates, n, err)) {
+       /* Fail if a refname appears more than once in the transaction: */
+       for (i = 0; i < n; i++)
+               string_list_append(&affected_refnames, updates[i]->refname);
+       string_list_sort(&affected_refnames);
+       if (ref_update_reject_duplicates(&affected_refnames, err)) {
                ret = TRANSACTION_GENERIC_ERROR;
                goto cleanup;
        }
 
-       /* Acquire all locks while verifying old values */
+       /*
+        * Acquire all locks, verify old values if provided, check
+        * that new values are valid, and write new values to the
+        * lockfiles, ready to be activated. Only keep one lockfile
+        * open at a time to avoid running out of file descriptors.
+        */
        for (i = 0; i < n; i++) {
                struct ref_update *update = updates[i];
-               int flags = update->flags;
-
-               if (is_null_sha1(update->new_sha1))
-                       flags |= REF_DELETING;
-               update->lock = lock_ref_sha1_basic(update->refname,
-                                                  (update->have_old ?
-                                                   update->old_sha1 :
-                                                   NULL),
-                                                  NULL,
-                                                  flags,
-                                                  &update->type);
+
+               if ((update->flags & REF_HAVE_NEW) &&
+                   is_null_sha1(update->new_sha1))
+                       update->flags |= REF_DELETING;
+               update->lock = lock_ref_sha1_basic(
+                               update->refname,
+                               ((update->flags & REF_HAVE_OLD) ?
+                                update->old_sha1 : NULL),
+                               &affected_refnames, NULL,
+                               update->flags,
+                               &update->type,
+                               err);
                if (!update->lock) {
+                       char *reason;
+
                        ret = (errno == ENOTDIR)
                                ? TRANSACTION_NAME_CONFLICT
                                : TRANSACTION_GENERIC_ERROR;
-                       strbuf_addf(err, "Cannot lock the ref '%s'.",
-                                   update->refname);
+                       reason = strbuf_detach(err, NULL);
+                       strbuf_addf(err, "cannot lock ref '%s': %s",
+                                   update->refname, reason);
+                       free(reason);
                        goto cleanup;
                }
+               if ((update->flags & REF_HAVE_NEW) &&
+                   !(update->flags & REF_DELETING)) {
+                       int overwriting_symref = ((update->type & REF_ISSYMREF) &&
+                                                 (update->flags & REF_NODEREF));
+
+                       if (!overwriting_symref &&
+                           !hashcmp(update->lock->old_oid.hash, update->new_sha1)) {
+                               /*
+                                * The reference already has the desired
+                                * value, so we don't need to write it.
+                                */
+                       } else if (write_ref_to_lockfile(update->lock,
+                                                        update->new_sha1)) {
+                               /*
+                                * The lock was freed upon failure of
+                                * write_ref_to_lockfile():
+                                */
+                               update->lock = NULL;
+                               strbuf_addf(err, "cannot update the ref '%s'.",
+                                           update->refname);
+                               ret = TRANSACTION_GENERIC_ERROR;
+                               goto cleanup;
+                       } else {
+                               update->flags |= REF_NEEDS_COMMIT;
+                       }
+               }
+               if (!(update->flags & REF_NEEDS_COMMIT)) {
+                       /*
+                        * We didn't have to write anything to the lockfile.
+                        * Close it to free up the file descriptor:
+                        */
+                       if (close_ref(update->lock)) {
+                               strbuf_addf(err, "Couldn't close %s.lock",
+                                           update->refname);
+                               goto cleanup;
+                       }
+               }
        }
 
        /* Perform updates first so live commits remain referenced */
        for (i = 0; i < n; i++) {
                struct ref_update *update = updates[i];
 
-               if (!is_null_sha1(update->new_sha1)) {
-                       if (write_ref_sha1(update->lock, update->new_sha1,
-                                          update->msg)) {
-                               update->lock = NULL; /* freed by write_ref_sha1 */
+               if (update->flags & REF_NEEDS_COMMIT) {
+                       if (commit_ref_update(update->lock,
+                                             update->new_sha1, update->msg)) {
+                               /* freed by commit_ref_update(): */
+                               update->lock = NULL;
                                strbuf_addf(err, "Cannot update the ref '%s'.",
                                            update->refname);
                                ret = TRANSACTION_GENERIC_ERROR;
                                goto cleanup;
+                       } else {
+                               /* freed by commit_ref_update(): */
+                               update->lock = NULL;
                        }
-                       update->lock = NULL; /* freed by write_ref_sha1 */
                }
        }
 
@@ -3798,7 +4072,7 @@ int ref_transaction_commit(struct ref_transaction *transaction,
        for (i = 0; i < n; i++) {
                struct ref_update *update = updates[i];
 
-               if (update->lock) {
+               if (update->flags & REF_DELETING) {
                        if (delete_ref_loose(update->lock, update->type, err)) {
                                ret = TRANSACTION_GENERIC_ERROR;
                                goto cleanup;
@@ -3825,6 +4099,99 @@ int ref_transaction_commit(struct ref_transaction *transaction,
                if (updates[i]->lock)
                        unlock_ref(updates[i]->lock);
        string_list_clear(&refs_to_delete, 0);
+       string_list_clear(&affected_refnames, 0);
+       return ret;
+}
+
+static int ref_present(const char *refname,
+                      const struct object_id *oid, int flags, void *cb_data)
+{
+       struct string_list *affected_refnames = cb_data;
+
+       return string_list_has_string(affected_refnames, refname);
+}
+
+int initial_ref_transaction_commit(struct ref_transaction *transaction,
+                                  struct strbuf *err)
+{
+       struct ref_dir *loose_refs = get_loose_refs(&ref_cache);
+       struct ref_dir *packed_refs = get_packed_refs(&ref_cache);
+       int ret = 0, i;
+       int n = transaction->nr;
+       struct ref_update **updates = transaction->updates;
+       struct string_list affected_refnames = STRING_LIST_INIT_NODUP;
+
+       assert(err);
+
+       if (transaction->state != REF_TRANSACTION_OPEN)
+               die("BUG: commit called for transaction that is not open");
+
+       /* Fail if a refname appears more than once in the transaction: */
+       for (i = 0; i < n; i++)
+               string_list_append(&affected_refnames, updates[i]->refname);
+       string_list_sort(&affected_refnames);
+       if (ref_update_reject_duplicates(&affected_refnames, err)) {
+               ret = TRANSACTION_GENERIC_ERROR;
+               goto cleanup;
+       }
+
+       /*
+        * It's really undefined to call this function in an active
+        * repository or when there are existing references: we are
+        * only locking and changing packed-refs, so (1) any
+        * simultaneous processes might try to change a reference at
+        * the same time we do, and (2) any existing loose versions of
+        * the references that we are setting would have precedence
+        * over our values. But some remote helpers create the remote
+        * "HEAD" and "master" branches before calling this function,
+        * so here we really only check that none of the references
+        * that we are creating already exists.
+        */
+       if (for_each_rawref(ref_present, &affected_refnames))
+               die("BUG: initial ref transaction called with existing refs");
+
+       for (i = 0; i < n; i++) {
+               struct ref_update *update = updates[i];
+
+               if ((update->flags & REF_HAVE_OLD) &&
+                   !is_null_sha1(update->old_sha1))
+                       die("BUG: initial ref transaction with old_sha1 set");
+               if (verify_refname_available(update->refname,
+                                            &affected_refnames, NULL,
+                                            loose_refs, err) ||
+                   verify_refname_available(update->refname,
+                                            &affected_refnames, NULL,
+                                            packed_refs, err)) {
+                       ret = TRANSACTION_NAME_CONFLICT;
+                       goto cleanup;
+               }
+       }
+
+       if (lock_packed_refs(0)) {
+               strbuf_addf(err, "unable to lock packed-refs file: %s",
+                           strerror(errno));
+               ret = TRANSACTION_GENERIC_ERROR;
+               goto cleanup;
+       }
+
+       for (i = 0; i < n; i++) {
+               struct ref_update *update = updates[i];
+
+               if ((update->flags & REF_HAVE_NEW) &&
+                   !is_null_sha1(update->new_sha1))
+                       add_packed_ref(update->refname, update->new_sha1);
+       }
+
+       if (commit_packed_refs()) {
+               strbuf_addf(err, "unable to commit packed-refs file: %s",
+                           strerror(errno));
+               ret = TRANSACTION_GENERIC_ERROR;
+               goto cleanup;
+       }
+
+cleanup:
+       transaction->state = REF_TRANSACTION_CLOSED;
+       string_list_clear(&affected_refnames, 0);
        return ret;
 }
 
@@ -3963,3 +4330,145 @@ int ref_is_hidden(const char *refname)
        }
        return 0;
 }
+
+struct expire_reflog_cb {
+       unsigned int flags;
+       reflog_expiry_should_prune_fn *should_prune_fn;
+       void *policy_cb;
+       FILE *newlog;
+       unsigned char last_kept_sha1[20];
+};
+
+static int expire_reflog_ent(unsigned char *osha1, unsigned char *nsha1,
+                            const char *email, unsigned long timestamp, int tz,
+                            const char *message, void *cb_data)
+{
+       struct expire_reflog_cb *cb = cb_data;
+       struct expire_reflog_policy_cb *policy_cb = cb->policy_cb;
+
+       if (cb->flags & EXPIRE_REFLOGS_REWRITE)
+               osha1 = cb->last_kept_sha1;
+
+       if ((*cb->should_prune_fn)(osha1, nsha1, email, timestamp, tz,
+                                  message, policy_cb)) {
+               if (!cb->newlog)
+                       printf("would prune %s", message);
+               else if (cb->flags & EXPIRE_REFLOGS_VERBOSE)
+                       printf("prune %s", message);
+       } else {
+               if (cb->newlog) {
+                       fprintf(cb->newlog, "%s %s %s %lu %+05d\t%s",
+                               sha1_to_hex(osha1), sha1_to_hex(nsha1),
+                               email, timestamp, tz, message);
+                       hashcpy(cb->last_kept_sha1, nsha1);
+               }
+               if (cb->flags & EXPIRE_REFLOGS_VERBOSE)
+                       printf("keep %s", message);
+       }
+       return 0;
+}
+
+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)
+{
+       static struct lock_file reflog_lock;
+       struct expire_reflog_cb cb;
+       struct ref_lock *lock;
+       char *log_file;
+       int status = 0;
+       int type;
+       struct strbuf err = STRBUF_INIT;
+
+       memset(&cb, 0, sizeof(cb));
+       cb.flags = flags;
+       cb.policy_cb = policy_cb_data;
+       cb.should_prune_fn = should_prune_fn;
+
+       /*
+        * The reflog file is locked by holding the lock on the
+        * reference itself, plus we might need to update the
+        * reference if --updateref was specified:
+        */
+       lock = lock_ref_sha1_basic(refname, sha1, NULL, NULL, 0, &type, &err);
+       if (!lock) {
+               error("cannot lock ref '%s': %s", refname, err.buf);
+               strbuf_release(&err);
+               return -1;
+       }
+       if (!reflog_exists(refname)) {
+               unlock_ref(lock);
+               return 0;
+       }
+
+       log_file = git_pathdup("logs/%s", refname);
+       if (!(flags & EXPIRE_REFLOGS_DRY_RUN)) {
+               /*
+                * Even though holding $GIT_DIR/logs/$reflog.lock has
+                * no locking implications, we use the lock_file
+                * machinery here anyway because it does a lot of the
+                * work we need, including cleaning up if the program
+                * exits unexpectedly.
+                */
+               if (hold_lock_file_for_update(&reflog_lock, log_file, 0) < 0) {
+                       struct strbuf err = STRBUF_INIT;
+                       unable_to_lock_message(log_file, errno, &err);
+                       error("%s", err.buf);
+                       strbuf_release(&err);
+                       goto failure;
+               }
+               cb.newlog = fdopen_lock_file(&reflog_lock, "w");
+               if (!cb.newlog) {
+                       error("cannot fdopen %s (%s)",
+                             reflog_lock.filename.buf, strerror(errno));
+                       goto failure;
+               }
+       }
+
+       (*prepare_fn)(refname, sha1, cb.policy_cb);
+       for_each_reflog_ent(refname, expire_reflog_ent, &cb);
+       (*cleanup_fn)(cb.policy_cb);
+
+       if (!(flags & EXPIRE_REFLOGS_DRY_RUN)) {
+               /*
+                * It doesn't make sense to adjust a reference pointed
+                * to by a symbolic ref based on expiring entries in
+                * the symbolic reference's reflog. Nor can we update
+                * a reference if there are no remaining reflog
+                * entries.
+                */
+               int update = (flags & EXPIRE_REFLOGS_UPDATE_REF) &&
+                       !(type & REF_ISSYMREF) &&
+                       !is_null_sha1(cb.last_kept_sha1);
+
+               if (close_lock_file(&reflog_lock)) {
+                       status |= error("couldn't write %s: %s", log_file,
+                                       strerror(errno));
+               } else if (update &&
+                          (write_in_full(lock->lk->fd,
+                               sha1_to_hex(cb.last_kept_sha1), 40) != 40 ||
+                        write_str_in_full(lock->lk->fd, "\n") != 1 ||
+                        close_ref(lock) < 0)) {
+                       status |= error("couldn't write %s",
+                                       lock->lk->filename.buf);
+                       rollback_lock_file(&reflog_lock);
+               } else if (commit_lock_file(&reflog_lock)) {
+                       status |= error("unable to commit reflog '%s' (%s)",
+                                       log_file, strerror(errno));
+               } else if (update && commit_ref(lock)) {
+                       status |= error("couldn't set %s", lock->ref_name);
+               }
+       }
+       free(log_file);
+       unlock_ref(lock);
+       return status;
+
+ failure:
+       rollback_lock_file(&reflog_lock);
+       free(log_file);
+       unlock_ref(lock);
+       return -1;
+}