code: func (t *Trashcan) Archive(filePath string) error {
  	return archiveFile(t.folderFs, t.versionsFs, filePath, func(name, tag string) string {
  		return name
  	})
  }
docs: // Archive moves the named file away to a version archive. If this function
  // returns nil, the named file does not exist any more (has been archived).