protected function merge(array $merge, array $config = []) {
    foreach ($merge as $path) {
      $merge = file_get_contents($path);
      $merge = str_replace('%paths.base%', dirname($path), $merge);
      $merge = Yaml::decode($merge);

      $config = NestedArray::mergeDeep($config, $merge);
    }
    return $config;
  }