/**
  * Return possible values for the named option
  *
  * @param string            $optionName Option name.
  * @param CompletionContext $context    Completion context.
  *
  * @return array
  */
 public function completeOptionValues($optionName, CompletionContext $context)
 {
     $ret = parent::completeOptionValues($optionName, $context);
     if ($optionName === 'extension') {
         return $this->_migrationManager->getMigrationFileExtensions();
     }
     return $ret;
 }