zTo = zBranch;
    zFrom = mprintf("root:%s", zBranch);
  }
  if( zCheckin!=0 && ( zFrom!=0 || zTo!=0 ) ){
    fossil_fatal("cannot use --checkin together with --from or --to");
  }
  g.diffCnt[0] = g.diffCnt[1] = g.diffCnt[2] = 0;
  if( 0==zCheckin ){
    if( zTo==0 || againstUndo ){
      db_must_be_within_tree();
    }else if( zFrom==0 ){
      fossil_fatal("must use --from if --to is present");
    }else{
      db_find_and_open_repository(0, 0);
    }
  }else{
    db_find_and_open_repository(0, 0);
  }
  diff_options(&DCfg, isGDiff, 0);
  determine_exec_relative_option(1);
  verify_all_options();
  if( g.argc>=3 ){