https://git-scm.com/book/en/v2
https://github.com/521xueweihan/git-tips
http://www.bootcss.com/p/git-guide/
https://www.liaoxuefeng.com/wiki/0013739516305929606dd18361248578c67b8067c8c017b000
http://danielkummer.github.io/git-flow-cheatsheet/index.zh_CN.html
https://www.git-tower.com/learn/git/ebook/cn/command-line/introduction