lib/input-generators/sitemap-index.js
function prepareWrite (outputPath, callback) {
  var path = pathLib.parse(outputPath);
  var dir = pathLib.join(path.root, path.dir);
  mkdirp(dir, callback);
}
function prepareWrite (outputPath, callback) {
  var path = pathLib.parse(outputPath);
  var dir = pathLib.join(path.root, path.dir);
  mkdirp(dir, callback);
}
function prepareWrite ( outputPath , callback ) { var path = pathLib . parse ( outputPath ) ; var dir = pathLib . join ( path . root , path . dir ) ; mkdirp ( dir , callback ) ; }
Make sure path exists so a sitemap write can succeed.

@param {String} outputPath - File path and name.
@param {Funcion} callback - Completion callback.
Make sure path exists so a sitemap write can succeed .