make deleting a missing ref more quiet

If git attempts to delete a ref, but the unlink of the ref
file fails, we print a message to stderr. This is usually a
good thing, but if the error is ENOENT, then it indicates
that the ref has _already_ been deleted. And since that's
our goal, it doesn't make sense to complain to the user.

This harmonizes the error reporting behavior for the
unpacked and packed cases; the packed case already printed
nothing on ENOENT, but the unpacked printed unconditionally.

Additionally, send-pack would, when deleting the tracking
ref corresponding to a remote delete, print "Failed to
delete" on any failure. This can be a misleading
message, since we actually _did_ delete at the remote side,
but we failed to delete locally. Rather than make the
message more precise, let's just eliminate it entirely; the
delete_ref routine already takes care of printing out a much
more specific message about what went wrong.

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

builtin-send-pack.c

@@ -226,8 +226,7 @@ static void update_tracking_ref(struct remote *remote, struct ref *ref)
 		if (args.verbose)
 			fprintf(stderr, "updating local tracking ref '%s'\n", rs.dst);
 		if (ref->deletion) {
-			if (delete_ref(rs.dst, NULL))
-				error("Failed to delete");
+			delete_ref(rs.dst, NULL);
 		} else
 			update_ref("update by push", rs.dst,
 					ref->new_sha1, NULL, 0, 0);

refs.c

@@ -925,7 +925,7 @@ int delete_ref(const char *refname, const unsigned char *sha1)
 		i = strlen(lock->lk->filename) - 5; /* .lock */
 		lock->lk->filename[i] = 0;
 		err = unlink(lock->lk->filename);
-		if (err) {
+		if (err && errno != ENOENT) {
 			ret = 1;
 			error("unlink(%s) failed: %s",
 			      lock->lk->filename, strerror(errno));

t/t5404-tracking-branches.sh

@@ -10,6 +10,7 @@ test_expect_success 'setup' '
 	git commit -m 1 &&
 	git branch b1 &&
 	git branch b2 &&
+	git branch b3 &&
 	git clone . aa &&
 	git checkout b1 &&
 	echo b1 >>file &&
@@ -50,4 +51,10 @@ test_expect_success 'deleted branches have their tracking branches removed' '
 	test "$(git rev-parse origin/b1)" = "origin/b1"
 '
 
+test_expect_success 'already deleted tracking branches ignored' '
+	git branch -d -r origin/b3 &&
+	git push origin :b3 >output 2>&1 &&
+	! grep error output
+'
+
 test_done