code: func New(dir string) (blobserver.Storage, error) {
  	var maxSize int64
  	if ok, _ := IsDir(dir); ok {
  		// TODO: detect existing max size from size of files, if obvious,
  		// and set maxSize to that?
  	}
  	return newStorage(dir, maxSize, nil)
  }
docs: // New returns a diskpacked storage implementation, adding blobs to
  // the provided directory. It doesn't delete any existing blob pack
  // files.