code: async function directoryContents (rootDir, filter, transform) {
    const items = await readdirAsync(rootDir)
    debug(`Directory contents [${items}]`)
    const statedItems = await Promise.all(
      items.map(async item => {
        const itemPath = path.join(rootDir, item)
        const stats = await lstatAsync(itemPath)
        return filter(stats) ? transform(itemPath, stats) : null
      })
    )
    const dirs = statedItems.filter(d => !!d)
    return dirs
  }
docs: filesUnder