code: func (ij *isolatedFile) item(h crypto.Hash) *Item {
  	return &Item{
  		Path:    ij.path,
  		RelPath: filepath.Base(ij.path),
  		Digest:  isolated.HashBytes(h, ij.json),
  		Size:    int64(len(ij.json)),
  	}
  }
docs: // item creates an *Item to represent the isolated JSON file.