code: func (gdw *NaiveDiffDriver) Changes(id, parent string) ([]archive.Change, error) {
  	driver := gdw.ProtoDriver
  
  	layerRootFs, err := driver.Get(id, "")
  	if err != nil {
  		return nil, err
  	}
  	defer driver.Put(id)
  
  	layerFs := layerRootFs.Path()
  	parentFs := ""
  
  	if parent != "" {
  		parentRootFs, err := driver.Get(parent, "")
  		if err != nil {
  			return nil, err
  		}
  		defer driver.Put(parent)
  		parentFs = parentRootFs.Path()
  	}
  
  	return archive.ChangesDirs(layerFs, parentFs)
  }
docs: // Changes produces a list of changes between the specified layer
  // and its parent layer. If parent is "", then all changes will be ADD changes.