code: func (s *storage) meta(br blob.Ref) (m blobMeta, err error) {
  	ms, err := s.index.Get(br.String())
  	if err != nil {
  		if err == sorted.ErrNotFound {
  			err = os.ErrNotExist
  		}
  		return
  	}
  	m, ok := parseBlobMeta(ms)
  	if !ok {
  		err = fmt.Errorf("diskpacked: bad blob metadata: %q", ms)
  	}
  	return
  }
docs: // meta fetches the metadata for the specified blob from the index.