code: func preservedFile(err error, path string, out io.Writer) error {
  	if len(path) > 0 {
  		if _, err := os.Stat(path); !os.IsNotExist(err) {
  			fmt.Fprintf(out, "A copy of your changes has been stored to %q\n", path)
  		}
  	}
  	return err
  }
docs: // preservedFile writes out a message about the provided file if it exists to the
  // provided output stream when an error happens. Used to notify the user where
  // their updates were preserved.