code: func (s *ObjectStorage) DeltaObject(t plumbing.ObjectType,
  	h plumbing.Hash) (plumbing.EncodedObject, error) {
  	obj, err := s.getFromUnpacked(h)
  	if err == plumbing.ErrObjectNotFound {
  		obj, err = s.getFromPackfile(h, true)
  	}
  
  	if err != nil {
  		return nil, err
  	}
  
  	if plumbing.AnyObject != t && obj.Type() != t {
  		return nil, plumbing.ErrObjectNotFound
  	}
  
  	return obj, nil
  }
docs: // DeltaObject returns the object with the given hash, by searching for
  // it in the packfile and the git object directories.