code: func hash(body string) string {
  	buf := sha256.New()
  	fmt.Fprintf(buf, "blob %d", len(body))
  	buf.Write([]byte{0})
  	buf.Write([]byte(body))
  	return "v2:" + hex.EncodeToString(buf.Sum(nil))
  }
docs: // hash returns generated ContentHash of a config file.