symbolic-ref: propagate error code from create_symref()

If create_symref() fails, git-symbolic-ref will still exit
with code 0, and our caller has no idea that the command did
nothing.

This appears to have been broken since the beginning of time
(e.g., it is not a regression where create_symref() stopped
calling die() or something similar).

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

builtin/symbolic-ref.c

@@ -67,7 +67,7 @@ int cmd_symbolic_ref(int argc, const char **argv, const char *prefix)
 		if (!strcmp(argv[0], "HEAD") &&
 		    !starts_with(argv[1], "refs/"))
 			die("Refusing to point HEAD outside of refs/");
-		create_symref(argv[0], argv[1], msg);
+		ret = !!create_symref(argv[0], argv[1], msg);
 		break;
 	default:
 		usage_with_options(git_symbolic_ref_usage, options);

t/t1401-symbolic-ref.sh

@@ -63,4 +63,10 @@ test_expect_success 'symbolic-ref fails to delete real ref' '
 '
 reset_to_sane
 
+test_expect_success 'symbolic-ref reports failure in exit code' '
+	test_when_finished "rm -f .git/HEAD.lock" &&
+	>.git/HEAD.lock &&
+	test_must_fail git symbolic-ref HEAD refs/heads/whatever
+'
+
 test_done