# File lib/directory_watcher/scanner.rb, line 94
  def run_once
    files = scan_files
    keys = [files.keys, @files.keys]  # current files, previous files

    find_added(files, *keys)
    find_modified(files, *keys)
    find_removed(*keys)

    notify
    @files = files    # store the current file list for the next iteration
    self
  end