code: func isRoot(path string) bool {
  	_, err := os.Stat(filepath.Join(path, "content", "welcome.article"))
  	if err == nil {
  		_, err = os.Stat(filepath.Join(path, "template", "index.tmpl"))
  	}
  	return err == nil
  }
docs: // isRoot reports whether path is the root directory of the tour tree.
  // To be the root, it must have content and template subdirectories.