builtin/ls-files: convert overlay_tree_on_cache to object_id

This is another caller of parse_tree_indirect.
Signed-off-by: Nbrian m. carlson <sandals@crustytoothpaste.net>
Signed-off-by: NJunio C Hamano <gitster@pobox.com>

builtin/ls-files.c

@@ -414,14 +414,14 @@ static void prune_cache(const char *prefix, size_t prefixlen)
 void overlay_tree_on_cache(const char *tree_name, const char *prefix)
 {
 	struct tree *tree;
-	unsigned char sha1[20];
+	struct object_id oid;
 	struct pathspec pathspec;
 	struct cache_entry *last_stage0 = NULL;
 	int i;
 
-	if (get_sha1(tree_name, sha1))
+	if (get_oid(tree_name, &oid))
 		die("tree-ish %s not found.", tree_name);
-	tree = parse_tree_indirect(sha1);
+	tree = parse_tree_indirect(oid.hash);
 	if (!tree)
 		die("bad tree-ish %s", tree_name);