- retval = ll_diff_tree_sha1(old, new, base, opt);
- if (!*base && DIFF_OPT_TST(opt, FOLLOW_RENAMES) && diff_might_be_rename())
- try_to_follow_renames(old, new, base, opt);
+ strbuf_init(&base, PATH_MAX);
+ strbuf_addstr(&base, base_str);
+
+ retval = ll_diff_tree_sha1(old, new, &base, opt);
+ if (!*base_str && DIFF_OPT_TST(opt, FOLLOW_RENAMES) && diff_might_be_rename())
+ try_to_follow_renames(old, new, &base, opt);
+
+ strbuf_release(&base);