code: func getWalkRoot(srcPath string, include string) string {
  	return srcPath + string(filepath.Separator) + include
  }
docs: // getWalkRoot calculates the root path when performing a TarWithOptions.
  // We use a separate function as this is platform specific. On Linux, we
  // can't use filepath.Join(srcPath,include) because this will clean away
  // a trailing "." or "/" which may be important.