/**
  * PUT admin/posts/{post}
  *
  * @param Post        $post
  * @param PostRequest $request
  * @return \Illuminate\Http\RedirectResponse|\Illuminate\Routing\Redirector
  */
 public function update(Post $post, PostRequest $request)
 {
     $post->update($request->all());
     if ($request->has('tag_list')) {
         $post->tags()->sync(Tag::findOrCreateMany($request->get('tag_list')));
     }
     flash()->success('The post has been updated');
     return redirect('/admin/posts');
 }