code: func (h *Handler) HasLegacySHA1() bool {
  	idx, ok := h.index.(*index.Index)
  	if !ok {
  		log.Printf("Cannot guess for legacy SHA1 because we don't have an *index.Index")
  		return false
  	}
  	ok, err := idx.HasLegacySHA1()
  	if err != nil {
  		log.Printf("Cannot guess for legacy SHA1: %v", err)
  		return false
  	}
  	return ok
  }
docs: // HasLegacySHA1 reports whether the server has legacy SHA-1 blobs indexed.