code: func NewReferenceStorage(base, temporal storer.ReferenceStorer) *ReferenceStorage {
  	return &ReferenceStorage{
  		ReferenceStorer: base,
  		temporal:        temporal,
  
  		deleted: make(map[plumbing.ReferenceName]struct{}, 0),
  	}
  }
docs: // NewReferenceStorage returns a new ReferenceStorer based on a base storer and
  // a temporal storer.