etcdserver/api/v2store/watcher_hub.go
func (wh *watcherHub) clone() *watcherHub {
	clonedHistory := wh.EventHistory.clone()

	return &watcherHub{
		EventHistory: clonedHistory,
	}
}
func (wh *watcherHub) clone() *watcherHub {
	clonedHistory := wh.EventHistory.clone()

	return &watcherHub{
		EventHistory: clonedHistory,
	}
}
// clone function clones the watcherHub and return the cloned one.
// only clone the static content. do not clone the current watchers.