code: func FileExists(fs utilfs.Filesystem, path string) (bool, error) {
  	if info, err := fs.Stat(path); err == nil {
  		if info.Mode().IsRegular() {
  			return true, nil
  		}
  		return false, fmt.Errorf("expected regular file at %q, but mode is %q", path, info.Mode().String())
  	} else if os.IsNotExist(err) {
  		return false, nil
  	} else {
  		return false, err
  	}
  }
docs: // FileExists returns true if a regular file exists at `path`, false if `path` does not exist, otherwise an error