code: func (b *Bundle) WatchFiles(watch bool) *Bundle {
  	if watch && b.err == nil && b.watcher == nil {
  		b.watcher, b.err = fsnotify.NewWatcher()
  	}
  	return b
  }
docs: // WatchFiles tells soy to watch any template files added to this bundle,
  // re-compile as necessary, and propagate the updates to your tofu.  It should
  // be called once, before adding any files.