1 files changed, 433 insertions, 334 deletions

diff --git a/refs.c b/refs.c
index 1491ae937e..32e91ff740 100644
--- a/refs.c
+++ b/refs.c
@@ -2,40 +2,65 @@
  * The backend-independent part of the reference module.
  */
 
-#include "cache.h"
+#include "git-compat-util.h"
+#include "advice.h"
 #include "config.h"
+#include "environment.h"
 #include "hashmap.h"
+#include "gettext.h"
+#include "hex.h"
 #include "lockfile.h"
 #include "iterator.h"
 #include "refs.h"
 #include "refs/refs-internal.h"
 #include "run-command.h"
 #include "hook.h"
-#include "object-store.h"
+#include "object-name.h"
+#include "object-store-ll.h"
 #include "object.h"
+#include "path.h"
 #include "tag.h"
 #include "submodule.h"
 #include "worktree.h"
 #include "strvec.h"
 #include "repository.h"
+#include "setup.h"
 #include "sigchain.h"
 #include "date.h"
 #include "commit.h"
+#include "wildmatch.h"
 
 /*
  * List of all available backends
  */
-static struct ref_storage_be *refs_backends = &refs_be_files;
+static const struct ref_storage_be *refs_backends[] = {
+	[REF_STORAGE_FORMAT_FILES] = &refs_be_files,
+	[REF_STORAGE_FORMAT_REFTABLE] = &refs_be_reftable,
+};
 
-static struct ref_storage_be *find_ref_storage_backend(const char *name)
+static const struct ref_storage_be *find_ref_storage_backend(unsigned int ref_storage_format)
 {
-	struct ref_storage_be *be;
-	for (be = refs_backends; be; be = be->next)
-		if (!strcmp(be->name, name))
-			return be;
+	if (ref_storage_format < ARRAY_SIZE(refs_backends))
+		return refs_backends[ref_storage_format];
 	return NULL;
 }
 
+unsigned int ref_storage_format_by_name(const char *name)
+{
+	for (unsigned int i = 0; i < ARRAY_SIZE(refs_backends); i++)
+		if (refs_backends[i] && !strcmp(refs_backends[i]->name, name))
+			return i;
+	return REF_STORAGE_FORMAT_UNKNOWN;
+}
+
+const char *ref_storage_format_to_name(unsigned int ref_storage_format)
+{
+	const struct ref_storage_be *be = find_ref_storage_backend(ref_storage_format);
+	if (!be)
+		return "unknown";
+	return be->name;
+}
+
 /*
  * How to handle various characters in refnames:
  * 0: An acceptable character for refs
@@ -359,35 +384,26 @@ char *refs_resolve_refdup(struct ref_store *refs,
 	return xstrdup_or_null(result);
 }
 
-char *resolve_refdup(const char *refname, int resolve_flags,
-		     struct object_id *oid, int *flags)
-{
-	return refs_resolve_refdup(get_main_ref_store(the_repository),
-				   refname, resolve_flags,
-				   oid, flags);
-}
-
-/* The argument to filter_refs */
-struct ref_filter {
+/* The argument to for_each_filter_refs */
+struct for_each_ref_filter {
 	const char *pattern;
 	const char *prefix;
 	each_ref_fn *fn;
 	void *cb_data;
 };
 
-int read_ref_full(const char *refname, int resolve_flags, struct object_id *oid, int *flags)
+int refs_read_ref_full(struct ref_store *refs, const char *refname,
+		       int resolve_flags, struct object_id *oid, int *flags)
 {
-	struct ref_store *refs = get_main_ref_store(the_repository);
-
 	if (refs_resolve_ref_unsafe(refs, refname, resolve_flags,
 				    oid, flags))
 		return 0;
 	return -1;
 }
 
-int read_ref(const char *refname, struct object_id *oid)
+int refs_read_ref(struct ref_store *refs, const char *refname, struct object_id *oid)
 {
-	return read_ref_full(refname, RESOLVE_REF_READING, oid, NULL);
+	return refs_read_ref_full(refs, refname, RESOLVE_REF_READING, oid, NULL);
 }
 
 int refs_ref_exists(struct ref_store *refs, const char *refname)
@@ -396,15 +412,11 @@ int refs_ref_exists(struct ref_store *refs, const char *refname)
 					 NULL, NULL);
 }
 
-int ref_exists(const char *refname)
+static int for_each_filter_refs(const char *refname,
+				const struct object_id *oid,
+				int flags, void *data)
 {
-	return refs_ref_exists(get_main_ref_store(the_repository), refname);
-}
-
-static int filter_refs(const char *refname, const struct object_id *oid,
-			   int flags, void *data)
-{
-	struct ref_filter *filter = (struct ref_filter *)data;
+	struct for_each_ref_filter *filter = data;
 
 	if (wildmatch(filter->pattern, refname, 0))
 		return 0;
@@ -451,7 +463,8 @@ static int warn_if_dangling_symref(const char *refname,
 	if (!(flags & REF_ISSYMREF))
 		return 0;
 
-	resolves_to = resolve_ref_unsafe(refname, 0, NULL, NULL);
+	resolves_to = refs_resolve_ref_unsafe(get_main_ref_store(the_repository),
+					      refname, 0, NULL, NULL);
 	if (!resolves_to
 	    || (d->refname
 		? strcmp(resolves_to, d->refname)
@@ -472,7 +485,8 @@ void warn_dangling_symref(FILE *fp, const char *msg_fmt, const char *refname)
 	data.refname = refname;
 	data.refnames = NULL;
 	data.msg_fmt = msg_fmt;
-	for_each_rawref(warn_if_dangling_symref, &data);
+	refs_for_each_rawref(get_main_ref_store(the_repository),
+			     warn_if_dangling_symref, &data);
 }
 
 void warn_dangling_symrefs(FILE *fp, const char *msg_fmt, const struct string_list *refnames)
@@ -483,7 +497,8 @@ void warn_dangling_symrefs(FILE *fp, const char *msg_fmt, const struct string_li
 	data.refname = NULL;
 	data.refnames = refnames;
 	data.msg_fmt = msg_fmt;
-	for_each_rawref(warn_if_dangling_symref, &data);
+	refs_for_each_rawref(get_main_ref_store(the_repository),
+			     warn_if_dangling_symref, &data);
 }
 
 int refs_for_each_tag_ref(struct ref_store *refs, each_ref_fn fn, void *cb_data)
@@ -491,32 +506,17 @@ 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 refs_for_each_tag_ref(get_main_ref_store(the_repository), 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 refs_for_each_branch_ref(get_main_ref_store(the_repository), 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 refs_for_each_remote_ref(get_main_ref_store(the_repository), fn, cb_data);
-}
-
-int head_ref_namespaced(each_ref_fn fn, void *cb_data)
+int refs_head_ref_namespaced(struct ref_store *refs, each_ref_fn fn, void *cb_data)
 {
 	struct strbuf buf = STRBUF_INIT;
 	int ret = 0;
@@ -524,7 +524,7 @@ int head_ref_namespaced(each_ref_fn fn, void *cb_data)
 	int flag;
 
 	strbuf_addf(&buf, "%sHEAD", get_git_namespace());
-	if (!read_ref_full(buf.buf, RESOLVE_REF_READING, &oid, &flag))
+	if (!refs_read_ref_full(refs, buf.buf, RESOLVE_REF_READING, &oid, &flag))
 		ret = fn(buf.buf, &oid, flag, cb_data);
 	strbuf_release(&buf);
 
@@ -557,11 +557,11 @@ void normalize_glob_ref(struct string_list_item *item, const char *prefix,
 	strbuf_release(&normalized_pattern);
 }
 
-int for_each_glob_ref_in(each_ref_fn fn, const char *pattern,
-	const char *prefix, void *cb_data)
+int refs_for_each_glob_ref_in(struct ref_store *refs, each_ref_fn fn,
+			      const char *pattern, const char *prefix, void *cb_data)
 {
 	struct strbuf real_pattern = STRBUF_INIT;
-	struct ref_filter filter;
+	struct for_each_ref_filter filter;
 	int ret;
 
 	if (!prefix && !starts_with(pattern, "refs/"))
@@ -581,15 +581,16 @@ int for_each_glob_ref_in(each_ref_fn fn, const char *pattern,
 	filter.prefix = prefix;
 	filter.fn = fn;
 	filter.cb_data = cb_data;
-	ret = for_each_ref(filter_refs, &filter);
+	ret = refs_for_each_ref(refs, for_each_filter_refs, &filter);
 
 	strbuf_release(&real_pattern);
 	return ret;
 }
 
-int for_each_glob_ref(each_ref_fn fn, const char *pattern, void *cb_data)
+int refs_for_each_glob_ref(struct ref_store *refs, each_ref_fn fn,
+			   const char *pattern, void *cb_data)
 {
-	return for_each_glob_ref_in(fn, pattern, NULL, cb_data);
+	return refs_for_each_glob_ref_in(refs, fn, pattern, NULL, cb_data);
 }
 
 const char *prettify_refname(const char *name)
@@ -834,6 +835,47 @@ static int is_pseudoref_syntax(const char *refname)
 	return 1;
 }
 
+int is_pseudoref(struct ref_store *refs, const char *refname)
+{
+	static const char *const irregular_pseudorefs[] = {
+		"AUTO_MERGE",
+		"BISECT_EXPECTED_REV",
+		"NOTES_MERGE_PARTIAL",
+		"NOTES_MERGE_REF",
+		"MERGE_AUTOSTASH",
+	};
+	struct object_id oid;
+	size_t i;
+
+	if (!is_pseudoref_syntax(refname))
+		return 0;
+
+	if (ends_with(refname, "_HEAD")) {
+		refs_resolve_ref_unsafe(refs, refname,
+					RESOLVE_REF_READING | RESOLVE_REF_NO_RECURSE,
+					&oid, NULL);
+		return !is_null_oid(&oid);
+	}
+
+	for (i = 0; i < ARRAY_SIZE(irregular_pseudorefs); i++)
+		if (!strcmp(refname, irregular_pseudorefs[i])) {
+			refs_resolve_ref_unsafe(refs, refname,
+						RESOLVE_REF_READING | RESOLVE_REF_NO_RECURSE,
+						&oid, NULL);
+			return !is_null_oid(&oid);
+		}
+
+	return 0;
+}
+
+int is_headref(struct ref_store *refs, const char *refname)
+{
+	if (!strcmp(refname, "HEAD"))
+		return refs_ref_exists(refs, refname);
+
+	return 0;
+}
+
 static int is_current_worktree_ref(const char *ref) {
 	return is_pseudoref_syntax(ref) || is_per_worktree_ref(ref);
 }
@@ -924,13 +966,6 @@ int refs_delete_ref(struct ref_store *refs, const char *msg,
 	return 0;
 }
 
-int delete_ref(const char *msg, const char *refname,
-	       const struct object_id *old_oid, unsigned int flags)
-{
-	return refs_delete_ref(get_main_ref_store(the_repository), msg, refname,
-			       old_oid, flags);
-}
-
 static void copy_reflog_msg(struct strbuf *sb, const char *msg)
 {
 	char c;
@@ -1013,55 +1048,40 @@ static int read_ref_at_ent(struct object_id *ooid, struct object_id *noid,
 			   const char *message, void *cb_data)
 {
 	struct read_ref_at_cb *cb = cb_data;
-	int reached_count;
 
 	cb->tz = tz;
 	cb->date = timestamp;
 
-	/*
-	 * It is not possible for cb->cnt == 0 on the first iteration because
-	 * that special case is handled in read_ref_at().
-	 */
-	if (cb->cnt > 0)
-		cb->cnt--;
-	reached_count = cb->cnt == 0 && !is_null_oid(ooid);
-	if (timestamp <= cb->at_time || reached_count) {
+	if (timestamp <= cb->at_time || cb->cnt == 0) {
 		set_read_ref_cutoffs(cb, timestamp, tz, message);
 		/*
 		 * we have not yet updated cb->[n|o]oid so they still
 		 * hold the values for the previous record.
 		 */
-		if (!is_null_oid(&cb->ooid) && !oideq(&cb->ooid, noid))
-			warning(_("log for ref %s has gap after %s"),
+		if (!is_null_oid(&cb->ooid)) {
+			oidcpy(cb->oid, noid);
+			if (!oideq(&cb->ooid, noid))
+				warning(_("log for ref %s has gap after %s"),
 					cb->refname, show_date(cb->date, cb->tz, DATE_MODE(RFC2822)));
-		if (reached_count)
-			oidcpy(cb->oid, ooid);
-		else if (!is_null_oid(&cb->ooid) || cb->date == cb->at_time)
+		}
+		else if (cb->date == cb->at_time)
 			oidcpy(cb->oid, noid);
 		else if (!oideq(noid, cb->oid))
 			warning(_("log for ref %s unexpectedly ended on %s"),
 				cb->refname, show_date(cb->date, cb->tz,
 						       DATE_MODE(RFC2822)));
+		cb->reccnt++;
+		oidcpy(&cb->ooid, ooid);
+		oidcpy(&cb->noid, noid);
 		cb->found_it = 1;
+		return 1;
 	}
 	cb->reccnt++;
 	oidcpy(&cb->ooid, ooid);
 	oidcpy(&cb->noid, noid);
-	return cb->found_it;
-}
-
-static int read_ref_at_ent_newest(struct object_id *ooid UNUSED,
-				  struct object_id *noid,
-				  const char *email UNUSED,
-				  timestamp_t timestamp, int tz,
-				  const char *message, void *cb_data)
-{
-	struct read_ref_at_cb *cb = cb_data;
-
-	set_read_ref_cutoffs(cb, timestamp, tz, message);
-	oidcpy(cb->oid, noid);
-	/* We just want the first entry */
-	return 1;
+	if (cb->cnt > 0)
+		cb->cnt--;
+	return 0;
 }
 
 static int read_ref_at_ent_oldest(struct object_id *ooid, struct object_id *noid,
@@ -1073,7 +1093,7 @@ static int read_ref_at_ent_oldest(struct object_id *ooid, struct object_id *noid
 
 	set_read_ref_cutoffs(cb, timestamp, tz, message);
 	oidcpy(cb->oid, ooid);
-	if (is_null_oid(cb->oid))
+	if (cb->at_time && is_null_oid(cb->oid))
 		oidcpy(cb->oid, noid);
 	/* We just want the first entry */
 	return 1;
@@ -1096,14 +1116,24 @@ int read_ref_at(struct ref_store *refs, const char *refname,
 	cb.cutoff_cnt = cutoff_cnt;
 	cb.oid = oid;
 
-	if (cb.cnt == 0) {
-		refs_for_each_reflog_ent_reverse(refs, refname, read_ref_at_ent_newest, &cb);
-		return 0;
-	}
-
 	refs_for_each_reflog_ent_reverse(refs, refname, read_ref_at_ent, &cb);
 
 	if (!cb.reccnt) {
+		if (cnt == 0) {
+			/*
+			 * The caller asked for ref@{0}, and we had no entries.
+			 * It's a bit subtle, but in practice all callers have
+			 * prepped the "oid" field with the current value of
+			 * the ref, which is the most reasonable fallback.
+			 *
+			 * We'll put dummy values into the out-parameters (so
+			 * they're not just uninitialized garbage), and the
+			 * caller can take our return value as a hint that
+			 * we did not find any such reflog.
+			 */
+			set_read_ref_cutoffs(&cb, 0, 0, "empty reflog");
+			return 1;
+		}
 		if (flags & GET_OID_QUIETLY)
 			exit(128);
 		else
@@ -1128,11 +1158,6 @@ struct ref_transaction *ref_store_transaction_begin(struct ref_store *refs,
 	return tr;
 }
 
-struct ref_transaction *ref_transaction_begin(struct strbuf *err)
-{
-	return ref_store_transaction_begin(get_main_ref_store(the_repository), err);
-}
-
 void ref_transaction_free(struct ref_transaction *transaction)
 {
 	size_t i;
@@ -1155,6 +1180,8 @@ void ref_transaction_free(struct ref_transaction *transaction)
 
 	for (i = 0; i < transaction->nr; i++) {
 		free(transaction->updates[i]->msg);
+		free((char *)transaction->updates[i]->new_target);
+		free((char *)transaction->updates[i]->old_target);
 		free(transaction->updates[i]);
 	}
 	free(transaction->updates);
@@ -1166,6 +1193,7 @@ struct ref_update *ref_transaction_add_update(
 		const char *refname, unsigned int flags,
 		const struct object_id *new_oid,
 		const struct object_id *old_oid,
+		const char *new_target, const char *old_target,
 		const char *msg)
 {
 	struct ref_update *update;
@@ -1173,16 +1201,24 @@ struct ref_update *ref_transaction_add_update(
 	if (transaction->state != REF_TRANSACTION_OPEN)
 		BUG("update called for transaction that is not open");
 
+	if (old_oid && old_target)
+		BUG("only one of old_oid and old_target should be non NULL");
+	if (new_oid && new_target)
+		BUG("only one of new_oid and new_target should be non NULL");
+
 	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)
+	update->new_target = xstrdup_or_null(new_target);
+	update->old_target = xstrdup_or_null(old_target);
+	if ((flags & REF_HAVE_NEW) && new_oid)
 		oidcpy(&update->new_oid, new_oid);
-	if (flags & REF_HAVE_OLD)
+	if ((flags & REF_HAVE_OLD) && old_oid)
 		oidcpy(&update->old_oid, old_oid);
+
 	update->msg = normalize_reflog_message(msg);
 	return update;
 }
@@ -1191,6 +1227,8 @@ int ref_transaction_update(struct ref_transaction *transaction,
 			   const char *refname,
 			   const struct object_id *new_oid,
 			   const struct object_id *old_oid,
+			   const char *new_target,
+			   const char *old_target,
 			   unsigned int flags, const char *msg,
 			   struct strbuf *err)
 {
@@ -1216,9 +1254,11 @@ int ref_transaction_update(struct ref_transaction *transaction,
 	flags &= REF_TRANSACTION_UPDATE_ALLOWED_FLAGS;
 
 	flags |= (new_oid ? REF_HAVE_NEW : 0) | (old_oid ? REF_HAVE_OLD : 0);
+	flags |= (new_target ? REF_HAVE_NEW : 0) | (old_target ? REF_HAVE_OLD : 0);
 
 	ref_transaction_add_update(transaction, refname, flags,
-				   new_oid, old_oid, msg);
+				   new_oid, old_oid, new_target,
+				   old_target, msg);
 	return 0;
 }
 
@@ -1233,7 +1273,8 @@ int ref_transaction_create(struct ref_transaction *transaction,
 		return 1;
 	}
 	return ref_transaction_update(transaction, refname, new_oid,
-				      null_oid(), flags, msg, err);
+				      null_oid(), NULL, NULL, flags,
+				      msg, err);
 }
 
 int ref_transaction_delete(struct ref_transaction *transaction,
@@ -1246,7 +1287,8 @@ int ref_transaction_delete(struct ref_transaction *transaction,
 		BUG("delete called with old_oid set to zeros");
 	return ref_transaction_update(transaction, refname,
 				      null_oid(), old_oid,
-				      flags, msg, err);
+				      NULL, NULL, flags,
+				      msg, err);
 }
 
 int ref_transaction_verify(struct ref_transaction *transaction,
@@ -1259,6 +1301,7 @@ int ref_transaction_verify(struct ref_transaction *transaction,
 		BUG("verify called with old_oid set to NULL");
 	return ref_transaction_update(transaction, refname,
 				      NULL, old_oid,
+				      NULL, NULL,
 				      flags, NULL, err);
 }
 
@@ -1273,8 +1316,8 @@ int refs_update_ref(struct ref_store *refs, const char *msg,
 
 	t = ref_store_transaction_begin(refs, &err);
 	if (!t ||
-	    ref_transaction_update(t, refname, new_oid, old_oid, flags, msg,
-				   &err) ||
+	    ref_transaction_update(t, refname, new_oid, old_oid, NULL, NULL,
+				   flags, msg, &err) ||
 	    ref_transaction_commit(t, &err)) {
 		ret = 1;
 		ref_transaction_free(t);
@@ -1301,74 +1344,68 @@ int refs_update_ref(struct ref_store *refs, const char *msg,
 	return 0;
 }
 
-int update_ref(const char *msg, const char *refname,
-	       const struct object_id *new_oid,
-	       const struct object_id *old_oid,
-	       unsigned int flags, enum action_on_err onerr)
+/*
+ * Check that the string refname matches a rule of the form
+ * "{prefix}%.*s{suffix}". So "foo/bar/baz" would match the rule
+ * "foo/%.*s/baz", and return the string "bar".
+ */
+static const char *match_parse_rule(const char *refname, const char *rule,
+				    size_t *len)
 {
-	return refs_update_ref(get_main_ref_store(the_repository), msg, refname, new_oid,
-			       old_oid, flags, onerr);
+	/*
+	 * Check that rule matches refname up to the first percent in the rule.
+	 * We can bail immediately if not, but otherwise we leave "rule" at the
+	 * %-placeholder, and "refname" at the start of the potential matched
+	 * name.
+	 */
+	while (*rule != '%') {
+		if (!*rule)
+			BUG("rev-parse rule did not have percent");
+		if (*refname++ != *rule++)
+			return NULL;
+	}
+
+	/*
+	 * Check that our "%" is the expected placeholder. This assumes there
+	 * are no other percents (placeholder or quoted) in the string, but
+	 * that is sufficient for our rev-parse rules.
+	 */
+	if (!skip_prefix(rule, "%.*s", &rule))
+		return NULL;
+
+	/*
+	 * And now check that our suffix (if any) matches.
+	 */
+	if (!strip_suffix(refname, rule, len))
+		return NULL;
+
+	return refname; /* len set by strip_suffix() */
 }
 
 char *refs_shorten_unambiguous_ref(struct ref_store *refs,
 				   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) {
-		/*
-		 * Pre-generate scanf formats from ref_rev_parse_rules[].
-		 * Generate a format suitable for scanf from a
-		 * ref_rev_parse_rules rule by interpolating "%s" at the
-		 * location of the "%.*s".
-		 */
-		size_t total_len = 0;
-		size_t offset = 0;
-
-		/* the rule list is NULL terminated, count them first */
-		for (nr_rules = 0; ref_rev_parse_rules[nr_rules]; nr_rules++)
-			/* -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(sizeof(char *), nr_rules), total_len));
-
-		offset = 0;
-		for (i = 0; i < nr_rules; i++) {
-			assert(offset < total_len);
-			scanf_fmts[i] = (char *)&scanf_fmts[nr_rules] + offset;
-			offset += xsnprintf(scanf_fmts[i], total_len - offset,
-					    ref_rev_parse_rules[i], 2, "%s") + 1;
-		}
-	}
-
-	/* bail out if there are no rules */
-	if (!nr_rules)
-		return xstrdup(refname);
-
-	/* buffer for scanf result, at most refname must fit */
-	short_name = xstrdup(refname);
-
 	/* skip first rule, it will always match */
-	for (i = nr_rules - 1; i > 0 ; --i) {
+	for (i = NUM_REV_PARSE_RULES - 1; i > 0 ; --i) {
 		int j;
 		int rules_to_fail = i;
-		int short_name_len;
+		const char *short_name;
+		size_t short_name_len;
 
-		if (1 != sscanf(refname, scanf_fmts[i], short_name))
+		short_name = match_parse_rule(refname, ref_rev_parse_rules[i],
+					      &short_name_len);
+		if (!short_name)
 			continue;
 
-		short_name_len = strlen(short_name);
-
 		/*
 		 * in strict mode, all (except the matched one) rules
 		 * must fail to resolve to a valid non-ambiguous ref
 		 */
 		if (strict)
-			rules_to_fail = nr_rules;
+			rules_to_fail = NUM_REV_PARSE_RULES;
 
 		/*
 		 * check if the short name resolves to a valid ref,
@@ -1388,7 +1425,8 @@ char *refs_shorten_unambiguous_ref(struct ref_store *refs,
 			 */
 			strbuf_reset(&resolved_buf);
 			strbuf_addf(&resolved_buf, rule,
-				    short_name_len, short_name);
+				    cast_size_t_to_int(short_name_len),
+				    short_name);
 			if (refs_ref_exists(refs, resolved_buf.buf))
 				break;
 		}
@@ -1399,24 +1437,16 @@ char *refs_shorten_unambiguous_ref(struct ref_store *refs,
 		 */
 		if (j == rules_to_fail) {
 			strbuf_release(&resolved_buf);
-			return short_name;
+			return xmemdupz(short_name, short_name_len);
 		}
 	}
 
 	strbuf_release(&resolved_buf);
-	free(short_name);
 	return xstrdup(refname);
 }
 
-char *shorten_unambiguous_ref(const char *refname, int strict)
-{
-	return refs_shorten_unambiguous_ref(get_main_ref_store(the_repository),
-					    refname, strict);
-}
-
-static struct string_list *hide_refs;
-
-int parse_hide_refs_config(const char *var, const char *value, const char *section)
+int parse_hide_refs_config(const char *var, const char *value, const char *section,
+			   struct strvec *hide_refs)
 {
 	const char *key;
 	if (!strcmp("transfer.hiderefs", var) ||
@@ -1427,27 +1457,23 @@ int parse_hide_refs_config(const char *var, const char *value, const char *secti
 
 		if (!value)
 			return config_error_nonbool(var);
-		ref = xstrdup(value);
+
+		/* drop const to remove trailing '/' characters */
+		ref = (char *)strvec_push(hide_refs, value);
 		len = strlen(ref);
 		while (len && ref[len - 1] == '/')
 			ref[--len] = '\0';
-		if (!hide_refs) {
-			CALLOC_ARRAY(hide_refs, 1);
-			hide_refs->strdup_strings = 1;
-		}
-		string_list_append(hide_refs, ref);
 	}
 	return 0;
 }
 
-int ref_is_hidden(const char *refname, const char *refname_full)
+int ref_is_hidden(const char *refname, const char *refname_full,
+		  const struct strvec *hide_refs)
 {
 	int i;
 
-	if (!hide_refs)
-		return 0;
 	for (i = hide_refs->nr - 1; i >= 0; i--) {
-		const char *match = hide_refs->items[i].string;
+		const char *match = hide_refs->v[i];
 		const char *subject;
 		int neg = 0;
 		const char *p;
@@ -1473,6 +1499,30 @@ int ref_is_hidden(const char *refname, const char *refname_full)
 	return 0;
 }
 
+const char **hidden_refs_to_excludes(const struct strvec *hide_refs)
+{
+	const char **pattern;
+	for (pattern = hide_refs->v; *pattern; pattern++) {
+		/*
+		 * We can't feed any excludes from hidden refs config
+		 * sections, since later rules may override previous
+		 * ones. For example, with rules "refs/foo" and
+		 * "!refs/foo/bar", we should show "refs/foo/bar" (and
+		 * everything underneath it), but the earlier exclusion
+		 * would cause us to skip all of "refs/foo".  We
+		 * likewise don't implement the namespace stripping
+		 * required for '^' rules.
+		 *
+		 * Both are possible to do, but complicated, so avoid
+		 * populating the jump list at all if we see either of
+		 * these patterns.
+		 */
+		if (**pattern == '!' || **pattern == '^')
+			return NULL;
+	}
+	return hide_refs->v;
+}
+
 const char *find_descendant_ref(const char *dirname,
 				const struct string_list *extras,
 				const struct string_list *skip)
@@ -1513,14 +1563,11 @@ int refs_head_ref(struct ref_store *refs, each_ref_fn fn, void *cb_data)
 	return 0;
 }
 
-int head_ref(each_ref_fn fn, void *cb_data)
-{
-	return refs_head_ref(get_main_ref_store(the_repository), fn, cb_data);
-}
-
 struct ref_iterator *refs_ref_iterator_begin(
 		struct ref_store *refs,
-		const char *prefix, int trim,
+		const char *prefix,
+		const char **exclude_patterns,
+		int trim,
 		enum do_for_each_ref_flags flags)
 {
 	struct ref_iterator *iter;
@@ -1536,8 +1583,7 @@ struct ref_iterator *refs_ref_iterator_begin(
 		}
 	}
 
-	iter = refs->be->iterator_begin(refs, prefix, flags);
-
+	iter = refs->be->iterator_begin(refs, prefix, exclude_patterns, flags);
 	/*
 	 * `iterator_begin()` already takes care of prefix, but we
 	 * might need to do some trimming:
@@ -1545,10 +1591,6 @@ struct ref_iterator *refs_ref_iterator_begin(
 	if (trim)
 		iter = prefix_ref_iterator_begin(iter, "", trim);
 
-	/* Sanity check for subclasses: */
-	if (!iter->ordered)
-		BUG("reference iterator is not ordered");
-
 	return iter;
 }
 
@@ -1571,7 +1613,7 @@ static int do_for_each_repo_ref(struct repository *r, const char *prefix,
 	if (!refs)
 		return 0;
 
-	iter = refs_ref_iterator_begin(refs, prefix, trim, flags);
+	iter = refs_ref_iterator_begin(refs, prefix, NULL, trim, flags);
 
 	return do_for_each_repo_ref_iterator(r, iter, fn, cb_data);
 }
@@ -1581,7 +1623,7 @@ struct do_for_each_ref_help {
 	void *cb_data;
 };
 
-static int do_for_each_ref_helper(struct repository *r,
+static int do_for_each_ref_helper(struct repository *r UNUSED,
 				  const char *refname,
 				  const struct object_id *oid,
 				  int flags,
@@ -1593,6 +1635,7 @@ static int do_for_each_ref_helper(struct repository *r,
 }
 
 static int do_for_each_ref(struct ref_store *refs, const char *prefix,
+			   const char **exclude_patterns,
 			   each_ref_fn fn, int trim,
 			   enum do_for_each_ref_flags flags, void *cb_data)
 {
@@ -1602,7 +1645,8 @@ static int do_for_each_ref(struct ref_store *refs, const char *prefix,
 	if (!refs)
 		return 0;
 
-	iter = refs_ref_iterator_begin(refs, prefix, trim, flags);
+	iter = refs_ref_iterator_begin(refs, prefix, exclude_patterns, trim,
+				       flags);
 
 	return do_for_each_repo_ref_iterator(the_repository, iter,
 					do_for_each_ref_helper, &hp);
@@ -1610,35 +1654,20 @@ static int do_for_each_ref(struct ref_store *refs, const char *prefix,
 
 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 refs_for_each_ref(get_main_ref_store(the_repository), fn, cb_data);
+	return do_for_each_ref(refs, "", NULL, fn, 0, 0, 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 refs_for_each_ref_in(get_main_ref_store(the_repository), prefix, fn, cb_data);
-}
-
-int for_each_fullref_in(const char *prefix, each_ref_fn fn, void *cb_data)
-{
-	return do_for_each_ref(get_main_ref_store(the_repository),
-			       prefix, fn, 0, 0, cb_data);
+	return do_for_each_ref(refs, prefix, NULL, fn, strlen(prefix), 0, cb_data);
 }
 
 int refs_for_each_fullref_in(struct ref_store *refs, const char *prefix,
+			     const char **exclude_patterns,
 			     each_ref_fn fn, void *cb_data)
 {
-	return do_for_each_ref(refs, prefix, fn, 0, 0, cb_data);
+	return do_for_each_ref(refs, prefix, exclude_patterns, fn, 0, 0, cb_data);
 }
 
 int for_each_replace_ref(struct repository *r, each_repo_ref_fn fn, void *cb_data)
@@ -1649,26 +1678,29 @@ int for_each_replace_ref(struct repository *r, each_repo_ref_fn fn, void *cb_dat
 				    DO_FOR_EACH_INCLUDE_BROKEN, cb_data);
 }
 
-int for_each_namespaced_ref(each_ref_fn fn, void *cb_data)
+int refs_for_each_namespaced_ref(struct ref_store *refs,
+				 const char **exclude_patterns,
+				 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(get_main_ref_store(the_repository),
-			      buf.buf, fn, 0, 0, cb_data);
+	ret = do_for_each_ref(refs, buf.buf, exclude_patterns, fn, 0, 0, cb_data);
 	strbuf_release(&buf);
 	return ret;
 }
 
 int refs_for_each_rawref(struct ref_store *refs, each_ref_fn fn, void *cb_data)
 {
-	return do_for_each_ref(refs, "", fn, 0,
+	return do_for_each_ref(refs, "", NULL, fn, 0,
 			       DO_FOR_EACH_INCLUDE_BROKEN, cb_data);
 }
 
-int for_each_rawref(each_ref_fn fn, void *cb_data)
+int refs_for_each_include_root_refs(struct ref_store *refs, each_ref_fn fn,
+				    void *cb_data)
 {
-	return refs_for_each_rawref(get_main_ref_store(the_repository), fn, cb_data);
+	return do_for_each_ref(refs, "", NULL, fn, 0,
+			       DO_FOR_EACH_INCLUDE_ROOT_REFS, cb_data);
 }
 
 static int qsort_strcmp(const void *va, const void *vb)
@@ -1729,9 +1761,11 @@ static void find_longest_prefixes(struct string_list *out,
 	strbuf_release(&prefix);
 }
 
-int for_each_fullref_in_prefixes(const char *namespace,
-				 const char **patterns,
-				 each_ref_fn fn, void *cb_data)
+int refs_for_each_fullref_in_prefixes(struct ref_store *ref_store,
+				      const char *namespace,
+				      const char **patterns,
+				      const char **exclude_patterns,
+				      each_ref_fn fn, void *cb_data)
 {
 	struct string_list prefixes = STRING_LIST_INIT_DUP;
 	struct string_list_item *prefix;
@@ -1746,7 +1780,8 @@ int for_each_fullref_in_prefixes(const char *namespace,
 
 	for_each_string_list_item(prefix, &prefixes) {
 		strbuf_addstr(&buf, prefix->string);
-		ret = for_each_fullref_in(buf.buf, fn, cb_data);
+		ret = refs_for_each_fullref_in(ref_store, buf.buf,
+					       exclude_patterns, fn, cb_data);
 		if (ret)
 			break;
 		strbuf_setlen(&buf, namespace_len);
@@ -1767,8 +1802,10 @@ static int refs_read_special_head(struct ref_store *ref_store,
 	int result = -1;
 	strbuf_addf(&full_path, "%s/%s", ref_store->gitdir, refname);
 
-	if (strbuf_read_file(&content, full_path.buf, 0) < 0)
+	if (strbuf_read_file(&content, full_path.buf, 0) < 0) {
+		*failure_errno = errno;
 		goto done;
+	}
 
 	result = parse_loose_ref_contents(content.buf, oid, referent, type,
 					  failure_errno);
@@ -1779,15 +1816,45 @@ done:
 	return result;
 }
 
+static int is_special_ref(const char *refname)
+{
+	/*
+	 * Special references are refs that have different semantics compared
+	 * to "normal" refs. These refs can thus not be stored in the ref
+	 * backend, but must always be accessed via the filesystem. The
+	 * following refs are special:
+	 *
+	 * - FETCH_HEAD may contain multiple object IDs, and each one of them
+	 *   carries additional metadata like where it came from.
+	 *
+	 * - MERGE_HEAD may contain multiple object IDs when merging multiple
+	 *   heads.
+	 *
+	 * Reading, writing or deleting references must consistently go either
+	 * through the filesystem (special refs) or through the reference
+	 * backend (normal ones).
+	 */
+	static const char * const special_refs[] = {
+		"FETCH_HEAD",
+		"MERGE_HEAD",
+	};
+	size_t i;
+
+	for (i = 0; i < ARRAY_SIZE(special_refs); i++)
+		if (!strcmp(refname, special_refs[i]))
+			return 1;
+
+	return 0;
+}
+
 int refs_read_raw_ref(struct ref_store *ref_store, const char *refname,
 		      struct object_id *oid, struct strbuf *referent,
 		      unsigned int *type, int *failure_errno)
 {
 	assert(failure_errno);
-	if (!strcmp(refname, "FETCH_HEAD") || !strcmp(refname, "MERGE_HEAD")) {
+	if (is_special_ref(refname))
 		return refs_read_special_head(ref_store, refname, oid, referent,
 					      type, failure_errno);
-	}
 
 	return ref_store->be->read_raw_ref(ref_store, refname, oid, referent,
 					   type, failure_errno);
@@ -1823,7 +1890,7 @@ const char *refs_resolve_ref_unsafe(struct ref_store *refs,
 			return NULL;
 
 		/*
-		 * dwim_ref() uses REF_ISBROKEN to distinguish between
+		 * repo_dwim_ref() uses REF_ISBROKEN to distinguish between
 		 * missing refs and refs that were present but invalid,
 		 * to complain about the latter to stderr.
 		 *
@@ -1889,18 +1956,9 @@ const char *refs_resolve_ref_unsafe(struct ref_store *refs,
 }
 
 /* backend functions */
-int refs_init_db(struct strbuf *err)
+int refs_init_db(struct ref_store *refs, int flags, struct strbuf *err)
 {
-	struct ref_store *refs = get_main_ref_store(the_repository);
-
-	return refs->be->init_db(refs, err);
-}
-
-const char *resolve_ref_unsafe(const char *refname, int resolve_flags,
-			       struct object_id *oid, int *flags)
-{
-	return refs_resolve_ref_unsafe(get_main_ref_store(the_repository), refname,
-				       resolve_flags, oid, flags);
+	return refs->be->init_db(refs, flags, err);
 }
 
 int resolve_gitlink_ref(const char *submodule, const char *refname,
@@ -1990,12 +2048,12 @@ static struct ref_store *ref_store_init(struct repository *repo,
 					const char *gitdir,
 					unsigned int flags)
 {
-	const char *be_name = "files";
-	struct ref_storage_be *be = find_ref_storage_backend(be_name);
+	const struct ref_storage_be *be;
 	struct ref_store *refs;
 
+	be = find_ref_storage_backend(repo->ref_storage_format);
 	if (!be)
-		BUG("reference backend %s is unknown", be_name);
+		BUG("reference backend is unknown");
 
 	refs = be->init(repo, gitdir, flags);
 	return refs;
@@ -2126,9 +2184,9 @@ void base_ref_store_init(struct ref_store *refs, struct repository *repo,
 }
 
 /* backend functions */
-int refs_pack_refs(struct ref_store *refs, unsigned int flags)
+int refs_pack_refs(struct ref_store *refs, struct pack_refs_opts *opts)
 {
-	return refs->be->pack_refs(refs, flags);
+	return refs->be->pack_refs(refs, opts);
 }
 
 int peel_iterated_oid(const struct object_id *base, struct object_id *peeled)
@@ -2141,26 +2199,27 @@ int peel_iterated_oid(const struct object_id *base, struct object_id *peeled)
 	return peel_object(base, peeled) ? -1 : 0;
 }
 
-int refs_create_symref(struct ref_store *refs,
-		       const char *ref_target,
-		       const char *refs_heads_master,
-		       const char *logmsg)
+int refs_update_symref(struct ref_store *refs, const char *ref,
+		       const char *target, const char *logmsg)
 {
-	char *msg;
-	int retval;
+	struct ref_transaction *transaction;
+	struct strbuf err = STRBUF_INIT;
+	int ret = 0;
 
-	msg = normalize_reflog_message(logmsg);
-	retval = refs->be->create_symref(refs, ref_target, refs_heads_master,
-					 msg);
-	free(msg);
-	return retval;
-}
+	transaction = ref_store_transaction_begin(refs, &err);
+	if (!transaction ||
+	    ref_transaction_update(transaction, ref, NULL, NULL,
+				   target, NULL, REF_NO_DEREF,
+				   logmsg, &err) ||
+	    ref_transaction_commit(transaction, &err)) {
+		ret = error("%s", err.buf);
+	}
 
-int create_symref(const char *ref_target, const char *refs_heads_master,
-		  const char *logmsg)
-{
-	return refs_create_symref(get_main_ref_store(the_repository), ref_target,
-				  refs_heads_master, logmsg);
+	strbuf_release(&err);
+	if (transaction)
+		ref_transaction_free(transaction);
+
+	return ret;
 }
 
 int ref_update_reject_duplicates(struct string_list *refnames,
@@ -2213,10 +2272,22 @@ static int run_transaction_hook(struct ref_transaction *transaction,
 		struct ref_update *update = transaction->updates[i];
 
 		strbuf_reset(&buf);
-		strbuf_addf(&buf, "%s %s %s\n",
-			    oid_to_hex(&update->old_oid),
-			    oid_to_hex(&update->new_oid),
-			    update->refname);
+
+		if (!(update->flags & REF_HAVE_OLD))
+			strbuf_addf(&buf, "%s ", oid_to_hex(null_oid()));
+		else if (update->old_target)
+			strbuf_addf(&buf, "ref:%s ", update->old_target);
+		else
+			strbuf_addf(&buf, "%s ", oid_to_hex(&update->old_oid));
+
+		if (!(update->flags & REF_HAVE_NEW))
+			strbuf_addf(&buf, "%s ", oid_to_hex(null_oid()));
+		else if (update->new_target)
+			strbuf_addf(&buf, "ref:%s ", update->new_target);
+		else
+			strbuf_addf(&buf, "%s ", oid_to_hex(&update->new_oid));
+
+		strbuf_addf(&buf, "%s\n", update->refname);
 
 		if (write_in_full(proc.in, buf.buf, buf.len) < 0) {
 			if (errno != EPIPE) {
@@ -2401,7 +2472,7 @@ int refs_verify_refname_available(struct ref_store *refs,
 	strbuf_addstr(&dirname, refname + dirname.len);
 	strbuf_addch(&dirname, '/');
 
-	iter = refs_ref_iterator_begin(refs, dirname.buf, 0,
+	iter = refs_ref_iterator_begin(refs, dirname.buf, NULL, 0,
 				       DO_FOR_EACH_INCLUDE_BROKEN);
 	while ((ok = ref_iterator_advance(iter)) == ITER_OK) {
 		if (skip &&
@@ -2430,20 +2501,30 @@ cleanup:
 	return ret;
 }
 
-int refs_for_each_reflog(struct ref_store *refs, each_ref_fn fn, void *cb_data)
+struct do_for_each_reflog_help {
+	each_reflog_fn *fn;
+	void *cb_data;
+};
+
+static int do_for_each_reflog_helper(struct repository *r UNUSED,
+				     const char *refname,
+				     const struct object_id *oid UNUSED,
+				     int flags,
+				     void *cb_data)
+{
+	struct do_for_each_reflog_help *hp = cb_data;
+	return hp->fn(refname, hp->cb_data);
+}
+
+int refs_for_each_reflog(struct ref_store *refs, each_reflog_fn fn, void *cb_data)
 {
 	struct ref_iterator *iter;
-	struct do_for_each_ref_help hp = { fn, cb_data };
+	struct do_for_each_reflog_help hp = { fn, cb_data };
 
 	iter = refs->be->reflog_iterator_begin(refs);
 
 	return do_for_each_repo_ref_iterator(the_repository, iter,
-					     do_for_each_ref_helper, &hp);
-}
-
-int for_each_reflog(each_ref_fn fn, void *cb_data)
-{
-	return refs_for_each_reflog(get_main_ref_store(the_repository), fn, cb_data);
+					     do_for_each_reflog_helper, &hp);
 }
 
 int refs_for_each_reflog_ent_reverse(struct ref_store *refs,
@@ -2455,58 +2536,28 @@ int refs_for_each_reflog_ent_reverse(struct ref_store *refs,
 						     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(the_repository),
-						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(the_repository), 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(the_repository), refname);
-}
-
 int refs_create_reflog(struct ref_store *refs, const char *refname,
 		       struct strbuf *err)
 {
 	return refs->be->create_reflog(refs, refname, err);
 }
 
-int safe_create_reflog(const char *refname, struct strbuf *err)
-{
-	return refs_create_reflog(get_main_ref_store(the_repository), refname,
-				  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(the_repository), refname);
-}
-
 int refs_reflog_expire(struct ref_store *refs,
 		       const char *refname,
 		       unsigned int flags,
@@ -2520,19 +2571,6 @@ int refs_reflog_expire(struct ref_store *refs,
 				       cleanup_fn, policy_cb_data);
 }
 
-int reflog_expire(const char *refname,
-		  unsigned int flags,
-		  reflog_expiry_prepare_fn prepare_fn,
-		  reflog_expiry_should_prune_fn should_prune_fn,
-		  reflog_expiry_cleanup_fn cleanup_fn,
-		  void *policy_cb_data)
-{
-	return refs_reflog_expire(get_main_ref_store(the_repository),
-				  refname, flags,
-				  prepare_fn, should_prune_fn,
-				  cleanup_fn, policy_cb_data);
-}
-
 int initial_ref_transaction_commit(struct ref_transaction *transaction,
 				   struct strbuf *err)
 {
@@ -2560,19 +2598,55 @@ void ref_transaction_for_each_queued_update(struct ref_transaction *transaction,
 int refs_delete_refs(struct ref_store *refs, const char *logmsg,
 		     struct string_list *refnames, unsigned int flags)
 {
+	struct ref_transaction *transaction;
+	struct strbuf err = STRBUF_INIT;
+	struct string_list_item *item;
+	int ret = 0, failures = 0;
 	char *msg;
-	int retval;
+
+	if (!refnames->nr)
+		return 0;
 
 	msg = normalize_reflog_message(logmsg);
-	retval = refs->be->delete_refs(refs, msg, refnames, flags);
-	free(msg);
-	return retval;
-}
 
-int delete_refs(const char *msg, struct string_list *refnames,
-		unsigned int flags)
-{
-	return refs_delete_refs(get_main_ref_store(the_repository), msg, refnames, flags);
+	/*
+	 * Since we don't check the references' old_oids, the
+	 * individual updates can't fail, so we can pack all of the
+	 * updates into a single transaction.
+	 */
+	transaction = ref_store_transaction_begin(refs, &err);
+	if (!transaction) {
+		ret = error("%s", err.buf);
+		goto out;
+	}
+
+	for_each_string_list_item(item, refnames) {
+		ret = ref_transaction_delete(transaction, item->string,
+					     NULL, flags, msg, &err);
+		if (ret) {
+			warning(_("could not delete reference %s: %s"),
+				item->string, err.buf);
+			strbuf_reset(&err);
+			failures = 1;
+		}
+	}
+
+	ret = ref_transaction_commit(transaction, &err);
+	if (ret) {
+		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);
+	}
+
+out:
+	if (!ret && failures)
+		ret = -1;
+	ref_transaction_free(transaction);
+	strbuf_release(&err);
+	free(msg);
+	return ret;
 }
 
 int refs_rename_ref(struct ref_store *refs, const char *oldref,
@@ -2587,11 +2661,6 @@ int refs_rename_ref(struct ref_store *refs, const char *oldref,
 	return retval;
 }
 
-int rename_ref(const char *oldref, const char *newref, const char *logmsg)
-{
-	return refs_rename_ref(get_main_ref_store(the_repository), oldref, newref, logmsg);
-}
-
 int refs_copy_existing_ref(struct ref_store *refs, const char *oldref,
 		    const char *newref, const char *logmsg)
 {
@@ -2604,7 +2673,37 @@ int refs_copy_existing_ref(struct ref_store *refs, const char *oldref,
 	return retval;
 }
 
-int copy_existing_ref(const char *oldref, const char *newref, const char *logmsg)
+const char *ref_update_original_update_refname(struct ref_update *update)
+{
+	while (update->parent_update)
+		update = update->parent_update;
+
+	return update->refname;
+}
+
+int ref_update_has_null_new_value(struct ref_update *update)
 {
-	return refs_copy_existing_ref(get_main_ref_store(the_repository), oldref, newref, logmsg);
+	return !update->new_target && is_null_oid(&update->new_oid);
+}
+
+int ref_update_check_old_target(const char *referent, struct ref_update *update,
+				struct strbuf *err)
+{
+	if (!update->old_target)
+		BUG("called without old_target set");
+
+	if (!strcmp(referent, update->old_target))
+		return 0;
+
+	if (!strcmp(referent, ""))
+		strbuf_addf(err, "verifying symref target: '%s': "
+			    "reference is missing but expected %s",
+			    ref_update_original_update_refname(update),
+			    update->old_target);
+	else
+		strbuf_addf(err, "verifying symref target: '%s': "
+			    "is at %s but expected %s",
+			    ref_update_original_update_refname(update),
+			    referent, update->old_target);
+	return -1;
 }