code: func NewRootNode(idx *index.Index) noder.Noder {
  	const rootNode = ""
  
  	m := map[string]*node{rootNode: {isDir: true}}
  
  	for _, e := range idx.Entries {
  		parts := strings.Split(e.Name, string("/"))
  
  		var fullpath string
  		for _, part := range parts {
  			parent := fullpath
  			fullpath = path.Join(fullpath, part)
  
  			if _, ok := m[fullpath]; ok {
  				continue
  			}
  
  			n := &node{path: fullpath}
  			if fullpath == e.Name {
  				n.entry = e
  			} else {
  				n.isDir = true
  			}
  
  			m[n.path] = n
  			m[parent].children = append(m[parent].children, n)
  		}
  	}
  
  	return m[rootNode]
  }
docs: // NewRootNode returns the root node of a computed tree from a index.Index,