public function addConfig($config, $watcher)
  {
    if (!$this->root) {
      return;
    }
    $config = realpath($config);

    $filesystem = new Filesystem();
    $relativePath = $filesystem->makePathRelative($config, $this->root);
    if (substr($relativePath, 0, 2) == "..") {
      return;
    }

    if (!isset($this->configs[$watcher])) {
      $this->configs[$watcher] = array();
    }
    $this->configs[$watcher][] = $config;
  }