Allow git push to delete remote ref.

This allows you to say

	git send-pack $URL :refs/heads/$branch

to delete the named remote branch.  The refspec $src:$dst means
replace the destination ref with the object known as $src on the
local side, so this is a natural extension to make an empty $src
mean "No object" to delete the target.

Signed-off-by: Junio C Hamano <junkio@cox.net>

1 files changed, 30 insertions, 11 deletions

diff --git a/send-pack.c b/send-pack.c
index 447666665b..328dbbc16a 100644
--- a/send-pack.c
+++ b/send-pack.c
@@ -271,6 +271,7 @@ static int send_pack(int in, int out, int nr_refspec, char **refspec)
 	int new_refs;
 	int ret = 0;
 	int ask_for_status_report = 0;
+	int allow_deleting_refs = 0;
 	int expect_status_report = 0;
 
 	/* No funny business with the matcher */
@@ -280,6 +281,8 @@ static int send_pack(int in, int out, int nr_refspec, char **refspec)
 	/* Does the other end support the reporting? */
 	if (server_supports("report-status"))
 		ask_for_status_report = 1;
+	if (server_supports("delete-refs"))
+		allow_deleting_refs = 1;
 
 	/* match them up */
 	if (!remote_tail)
@@ -299,9 +302,19 @@ static int send_pack(int in, int out, int nr_refspec, char **refspec)
 	new_refs = 0;
 	for (ref = remote_refs; ref; ref = ref->next) {
 		char old_hex[60], *new_hex;
+		int delete_ref;
+
 		if (!ref->peer_ref)
 			continue;
-		if (!hashcmp(ref->old_sha1, ref->peer_ref->new_sha1)) {
+
+		delete_ref = is_null_sha1(ref->peer_ref->new_sha1);
+		if (delete_ref && !allow_deleting_refs) {
+			error("remote does not support deleting refs");
+			ret = -2;
+			continue;
+		}
+		if (!delete_ref &&
+		    !hashcmp(ref->old_sha1, ref->peer_ref->new_sha1)) {
 			if (verbose)
 				fprintf(stderr, "'%s': up-to-date\n", ref->name);
 			continue;
@@ -321,9 +334,13 @@ static int send_pack(int in, int out, int nr_refspec, char **refspec)
 		 *
 		 * (3) 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
+		 *     always allowed.
 		 */
 
 		if (!force_update &&
+		    !delete_ref &&
 		    !is_zero_sha1(ref->old_sha1) &&
 		    !ref->force) {
 			if (!has_sha1_file(ref->old_sha1) ||
@@ -347,12 +364,8 @@ static int send_pack(int in, int out, int nr_refspec, char **refspec)
 			}
 		}
 		hashcpy(ref->new_sha1, ref->peer_ref->new_sha1);
-		if (is_zero_sha1(ref->new_sha1)) {
-			error("cannot happen anymore");
-			ret = -3;
-			continue;
-		}
-		new_refs++;
+		if (!delete_ref)
+			new_refs++;
 		strcpy(old_hex, sha1_to_hex(ref->old_sha1));
 		new_hex = sha1_to_hex(ref->new_sha1);
 
@@ -366,10 +379,16 @@ static int send_pack(int in, int out, int nr_refspec, char **refspec)
 		else
 			packet_write(out, "%s %s %s",
 				     old_hex, new_hex, ref->name);
-		fprintf(stderr, "updating '%s'", ref->name);
-		if (strcmp(ref->name, ref->peer_ref->name))
-			fprintf(stderr, " using '%s'", ref->peer_ref->name);
-		fprintf(stderr, "\n  from %s\n  to   %s\n", old_hex, new_hex);
+		if (delete_ref)
+			fprintf(stderr, "deleting '%s'\n", ref->name);
+		else {
+			fprintf(stderr, "updating '%s'", ref->name);
+			if (strcmp(ref->name, ref->peer_ref->name))
+				fprintf(stderr, " using '%s'",
+					ref->peer_ref->name);
+			fprintf(stderr, "\n  from %s\n  to   %s\n",
+				old_hex, new_hex);
+		}
 	}
 
 	packet_flush(out);