Merge branch 'cn/maint-branch-with-bad'

* cn/maint-branch-with-bad:
  branch: don't assume the merge filter ref exists

Conflicts:
	t/t3200-branch.sh

builtin/branch.c

@@ -530,6 +530,10 @@ static int print_ref_list(int kinds, int detached, int verbose, int abbrev, stru
 	if (merge_filter != NO_FILTER) {
 		struct commit *filter;
 		filter = lookup_commit_reference_gently(merge_filter_ref, 0);
+		if (!filter)
+			die("object '%s' does not point to a commit",
+			    sha1_to_hex(merge_filter_ref));
+
 		filter->object.flags |= UNINTERESTING;
 		add_pending_object(&ref_list.revs,
 				   (struct object *) filter, "");

t/t3200-branch.sh

@@ -653,4 +653,8 @@ test_expect_success 'refuse --edit-description on unborn branch for now' '
 	)
 '
 
+test_expect_success '--merged catches invalid object names' '
+	test_must_fail git branch --merged 0000000000000000000000000000000000000000
+'
+
 test_done