public function add($all = true, $refspec = '', $force = false) {
    $command = $this->getResettedCommandBuilder()->addSubcommand('add')->addParam($refspec);
    if($all) {
      $command->addArgument('all');
    }
    if($force) {
      $command->addArgument('force');
    }
    $this->getRunnerWithDirectory()->run($command);
    return $this;
  }