class Lookbook::Reloaders::Reloader

def file_watcher
  return @_file_watcher if @_file_watcher
  to_watch = directories.each_with_object({}) do |directory, result|
    result[directory] = extensions
  end
  @_file_watcher ||= FileWatcher.new([], to_watch) do
    callback.call(@last_changes)
    @last_changes = nil
  end
end