code: func NewPackfile(index idxfile.Index, fs billy.Filesystem, file billy.File) *Packfile {
  	return NewPackfileWithCache(index, fs, file, cache.NewObjectLRUDefault())
  }
docs: // NewPackfile returns a packfile representation for the given packfile file
  // and packfile idx.
  // If the filesystem is provided, the packfile will return FSObjects, otherwise
  // it will return MemoryObjects.