code: func ApplyLayer(dest string, layer io.Reader) (size int64, err error) {
  	return applyLayerHandler(dest, layer, &archive.TarOptions{}, true)
  }
docs: // ApplyLayer parses a diff in the standard layer format from `layer`,
  // and applies it to the directory `dest`. The stream `layer` can only be
  // uncompressed.
  // Returns the size in bytes of the contents of the layer.