code: function treeFromPaths (files, baseDir, renderLabelFn, options = {}) {
    return {
      label: options.label || '',
      nodes: childNodesFromPaths(files, baseDir, renderLabelFn, files, baseDir)
    }
  }
docs: Transform an array of paths into an [archy](https://www.npmjs.com/package/archy)-compatible tree structure.
  
  ```
  ['abc/cde/efg/', 'abc/cde/abc', 'abc/zyx']
  ```
  becomes
  ```
  {
  label: 'abc/',
  nodes: [{ label: 'cde/',nodes: ['efg/', 'abc']}, 'zyx']
  }
  ```
  
  Nodes with a single subnode are collapsed and the resulting node gets the label `node/subnode`.
  
  @param {string[]} files an array of sorted file paths relative to `parent`
  @param {string} baseDir the directory of the files
  @param {function(parent:string, file:string, explicit: boolean):string} renderLabelFn function that renders the label
  of a node. It receives the parent and a filenpath as parameters.
  @param {object=} options optional parameters
  @param {string=} options.label the label of the root node (default: '')
  @returns {object} a tree structure as needed by [archy](https://www.npmjs.com/package/archy)
  @access private