code: func (tz *TzArchive) AddEmptyDir(dirPath string) bool {
  	if !strings.HasSuffix(dirPath, "/") {
  		dirPath += "/"
  	}
  
  	for _, f := range tz.files {
  		if dirPath == f.Name {
  			return false
  		}
  	}
  
  	dirPath = strings.TrimSuffix(dirPath, "/")
  	if strings.Contains(dirPath, "/") {
  		// Auto add all upper level directories.
  		tz.AddEmptyDir(path.Dir(dirPath))
  	}
  	tz.files = append(tz.files, &File{
  		Header: &tar.Header{
  			Name: dirPath + "/",
  		},
  	})
  	tz.updateStat()
  	return true
  }
docs: // AddEmptyDir adds a raw directory entry to TzArchive,
  // it returns false if same directory enry already existed.