code: func NewTreeRootNode(t *Tree) noder.Noder {
  	if t == nil {
  		return &treeNoder{}
  	}
  
  	return &treeNoder{
  		parent: t,
  		name:   "",
  		mode:   filemode.Dir,
  		hash:   t.Hash,
  	}
  }
docs: // NewTreeRootNode returns the root node of a Tree