/**
  * Format the given S3 configuration with the default options.
  *
  * @param array $config
  *
  * @return array
  */
 protected function formatS3Config(array $config)
 {
     $config += ['version' => 'latest'];
     if ($config['key'] && $config['secret']) {
         $config['credentials'] = Arr::only($config, ['key', 'secret']);
     }
     return $config;
 }