git 参考网站
https://www.liaoxuefeng.com/wiki/896043488029600
$ git clone git@github.com:michaelliao/gitskills.git
Cloning into 'gitskills'...
remote: Counting objects: 3, done.
remote: Total 3 (delta 0), reused 0 (delta 0), pack-reused 3
Receiving objects: 100% (3/3), done.