如何更新自己的fork以便包含别的collaborator的贡献?1. git remote add upstream <path_to_upstream_original_repo>;(add remote for upstream)2.git fetch upstream(fetch changes)3.git merge upstream/master master(merge them into local master)4.git push origin master(push your change to your remote fork)5.在github中执行pull request操作,以便把你的改动merge到upstream repo中去