"  --root        include the initial commit as diff against /dev/null\n"
 COMMON_DIFF_OPTIONS_HELP;
 
-int cmd_diff_tree(int argc, const char **argv, char **envp)
+int cmd_diff_tree(int argc, const char **argv, const char *prefix)
 {
        int nr_sha1;
        char line[1000];
        static struct rev_info *opt = &log_tree_opt;
        int read_stdin = 0;
 
-       git_config(git_diff_config);
+       init_revisions(opt, prefix);
+       git_config(git_default_config); /* no "diff" UI options */
        nr_sha1 = 0;
-       init_revisions(opt);
        opt->abbrev = 0;
        opt->diff = 1;
        argc = setup_revisions(argc, argv, opt, NULL);
        }
 
        if (!read_stdin)
-               return 0;
+               return opt->diffopt.exit_with_status ?
+                   opt->diffopt.has_changes: 0;
 
        if (opt->diffopt.detect_rename)
                opt->diffopt.setup |= (DIFF_SETUP_USE_SIZE_CACHE |
                else
                        diff_tree_stdin(line);
        }
-       return 0;
+       return opt->diffopt.exit_with_status ? opt->diffopt.has_changes: 0;
 }