refs.c: pass a skip list to name_conflict_fn

Allow passing a list of refs to skip checking to name_conflict_fn.
There are some conditions where we want to allow a temporary conflict and skip
checking those refs. For example if we have a transaction that
1, guarantees that m is a packed refs and there is no loose ref for m
2, the transaction will delete m from the packed ref
3, the transaction will create conflicting m/m

For this case we want to be able to lock and create m/m since we know that the
conflict is only transient. I.e. the conflict will be automatically resolved
by the transaction when it deletes m.

Signed-off-by: Ronnie Sahlberg <sahlberg@google.com>
Signed-off-by: Jonathan Nieder <jrnieder@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 28 insertions, 13 deletions

diff --git a/refs.c b/refs.c
index f124c2ba16..b63ab2f155 100644
--- a/refs.c
+++ b/refs.c
@@ -801,14 +801,16 @@ static int names_conflict(const char *refname1, const char *refname2)
 
 struct name_conflict_cb {
 	const char *refname;
-	const char *oldrefname;
 	const char *conflicting_refname;
+	struct string_list *skiplist;
 };
 
 static int name_conflict_fn(struct ref_entry *entry, void *cb_data)
 {
 	struct name_conflict_cb *data = (struct name_conflict_cb *)cb_data;
-	if (data->oldrefname && !strcmp(data->oldrefname, entry->name))
+
+	if (data->skiplist &&
+	    string_list_has_string(data->skiplist, entry->name))
 		return 0;
 	if (names_conflict(data->refname, entry->name)) {
 		data->conflicting_refname = entry->name;
@@ -822,15 +824,17 @@ static int name_conflict_fn(struct ref_entry *entry, void *cb_data)
  * conflicting with the name of an existing reference in dir.  If
  * oldrefname is non-NULL, ignore potential conflicts with oldrefname
  * (e.g., because oldrefname is scheduled for deletion in the same
- * operation).
+ * operation). skiplist contains a list of refs we want to skip checking for
+ * conflicts with. skiplist must be sorted.
  */
-static int is_refname_available(const char *refname, const char *oldrefname,
-				struct ref_dir *dir)
+static int is_refname_available(const char *refname,
+				struct ref_dir *dir,
+				struct string_list *skiplist)
 {
 	struct name_conflict_cb data;
 	data.refname = refname;
-	data.oldrefname = oldrefname;
 	data.conflicting_refname = NULL;
+	data.skiplist = skiplist;
 
 	sort_ref_dir(dir);
 	if (do_for_each_entry_in_dir(dir, 0, name_conflict_fn, &data)) {
@@ -2080,6 +2084,7 @@ 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,
+					    struct string_list *skiplist,
 					    int flags, int *type_p)
 {
 	char *ref_file;
@@ -2129,7 +2134,8 @@ static struct ref_lock *lock_ref_sha1_basic(const char *refname,
 	 * name is a proper prefix of our refname.
 	 */
 	if (missing &&
-	     !is_refname_available(refname, NULL, get_packed_refs(&ref_cache))) {
+	     !is_refname_available(refname, get_packed_refs(&ref_cache),
+				   skiplist)) {
 		last_errno = ENOTDIR;
 		goto error_return;
 	}
@@ -2187,7 +2193,7 @@ 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, flags, type_p);
+	return lock_ref_sha1_basic(refname, old_sha1, NULL, flags, type_p);
 }
 
 /*
@@ -2648,6 +2654,7 @@ 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 string_list skiplist = STRING_LIST_INIT_NODUP;
 
 	if (log && S_ISLNK(loginfo.st_mode))
 		return error("reflog for %s is a symlink", oldrefname);
@@ -2659,11 +2666,18 @@ int rename_ref(const char *oldrefname, const char *newrefname, const char *logms
 	if (!symref)
 		return error("refname %s not found", oldrefname);
 
-	if (!is_refname_available(newrefname, oldrefname, get_packed_refs(&ref_cache)))
+	string_list_insert(&skiplist, oldrefname);
+	if (!is_refname_available(newrefname, get_packed_refs(&ref_cache),
+				  &skiplist)) {
+		string_list_clear(&skiplist, 0);
 		return 1;
-
-	if (!is_refname_available(newrefname, oldrefname, get_loose_refs(&ref_cache)))
+	}
+	if (!is_refname_available(newrefname, get_loose_refs(&ref_cache),
+				  &skiplist)) {
+		string_list_clear(&skiplist, 0);
 		return 1;
+	}
+	string_list_clear(&skiplist, 0);
 
 	if (log && rename(git_path("logs/%s", oldrefname), git_path(TMP_RENAMED_LOG)))
 		return error("unable to move logfile logs/%s to "TMP_RENAMED_LOG": %s",
@@ -2692,7 +2706,7 @@ int rename_ref(const char *oldrefname, const char *newrefname, const char *logms
 
 	logmoved = log;
 
-	lock = lock_ref_sha1_basic(newrefname, NULL, 0, NULL);
+	lock = lock_ref_sha1_basic(newrefname, NULL, NULL, 0, NULL);
 	if (!lock) {
 		error("unable to lock %s for update", newrefname);
 		goto rollback;
@@ -2707,7 +2721,7 @@ int rename_ref(const char *oldrefname, const char *newrefname, const char *logms
 	return 0;
 
  rollback:
-	lock = lock_ref_sha1_basic(oldrefname, NULL, 0, NULL);
+	lock = lock_ref_sha1_basic(oldrefname, NULL, NULL, 0, NULL);
 	if (!lock) {
 		error("unable to lock %s for rollback", oldrefname);
 		goto rollbacklog;
@@ -3582,6 +3596,7 @@ int ref_transaction_commit(struct ref_transaction *transaction,
 						   (update->have_old ?
 						    update->old_sha1 :
 						    NULL),
+						   NULL,
 						   update->flags,
 						   &update->type);
 		if (!update->lock) {