push: require force for refs under refs/tags/

References are allowed to update from one commit-ish to another if the
former is an ancestor of the latter.  This behavior is oriented to
branches which are expected to move with commits.  Tag references are
expected to be static in a repository, though, thus an update to
something under refs/tags/ should be rejected unless the update is
forced.

Signed-off-by: Chris Rorvick <chris@rorvick.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 14 insertions, 4 deletions

diff --git a/remote.c b/remote.c
index 4a6f822089..012b52f6fd 100644
--- a/remote.c
+++ b/remote.c
@@ -1315,14 +1315,18 @@ void set_ref_status_for_push(struct ref *remote_refs, int send_mirror,
 		 *
 		 * (1) if the old thing does not exist, it is OK.
 		 *
-		 * (2) if you do not have the old thing, you are not allowed
+		 * (2) if the destination is under refs/tags/ you are
+		 *     not allowed to overwrite it; tags are expected
+		 *     to be static once created
+		 *
+		 * (3) if you do not have the old thing, you are not allowed
 		 *     to overwrite it; you would not know what you are losing
 		 *     otherwise.
 		 *
-		 * (3) if both new and old are commit-ish, and new is a
+		 * (4) if both new and old are commit-ish, and new is a
 		 *     descendant of old, it is OK.
 		 *
-		 * (4) regardless of all of the above, removing :B is
+		 * (5) regardless of all of the above, removing :B is
 		 *     always allowed.
 		 */
 
@@ -1337,7 +1341,13 @@ void set_ref_status_for_push(struct ref *remote_refs, int send_mirror,
 				!has_sha1_file(ref->old_sha1)
 				  || !ref_newer(ref->new_sha1, ref->old_sha1);
 
-			if (ref->nonfastforward) {
+			if (ref->not_forwardable) {
+				ref->requires_force = 1;
+				if (!force_ref_update) {
+					ref->status = REF_STATUS_REJECT_ALREADY_EXISTS;
+					continue;
+				}
+			} else if (ref->nonfastforward) {
 				ref->requires_force = 1;
 				if (!force_ref_update) {
 					ref->status = REF_STATUS_REJECT_NONFASTFORWARD;