line[len-1] = 0;
        if (get_sha1_hex(line, sha1))
                return -1;
-       obj = lookup_unknown_object(sha1);
-       if (!obj || !obj->parsed)
-               obj = parse_object(sha1);
+       obj = parse_object(sha1);
        if (!obj)
                return -1;
        if (obj->type == OBJ_COMMIT)
 
 static const char diff_tree_usage[] =
 "git diff-tree [--stdin] [-m] [-c] [--cc] [-s] [-v] [--pretty] [-t] [-r] [--root] "
-"[<common diff options>] <tree-ish> [<tree-ish>] [<path>...]\n"
+"[<common-diff-options>] <tree-ish> [<tree-ish>] [<path>...]\n"
 "  -r            diff recursively\n"
 "  --root        include the initial commit as diff against /dev/null\n"
 COMMON_DIFF_OPTIONS_HELP;