code: function dto(opts, cb) {
    opts = 'string' == typeof opts
      ? {path: opts}
      : opts
  
    const path = opts.path || process.cwd()
    cb = cb || function(){}
  
    assert.equal(typeof path, 'string')
    assert.equal(typeof cb, 'function')
  
    saveDirs(path, {}, function(err, res) {
      if (err) return cb(err)
      saveFiles(path, opts, res, cb)
    })
  }
docs: directory-to-object @param {Object|String} opts @param {Function} cb