directories_to_watch

# File activesupport/lib/active_support/evented_file_update_checker.rb, line 119
      def directories_to_watch
        dtw = (@files + @dirs.keys).map { |f| @ph.existing_parent(f) }
        dtw.compact!
        dtw.uniq!

        @ph.filter_out_descendants(dtw)
      end