function directoriesUnder (rootDir) {
  return directoryContents(
    rootDir,
    stats => stats.isDirectory(),
    (path, stats) => path
  )
}
function directoriesUnder (rootDir) {
  return directoryContents(
    rootDir,
    stats => stats.isDirectory(),
    (path, stats) => path
  )
}
function directoriesUnder ( rootDir ) { return directoryContents ( rootDir , stats => stats . isDirectory ( ) , ( path , stats ) => path ) }
collect
collect