git tag使用

參考:
* .6 Git 基礎 - 標籤
** REF: https://git-scm.com/book/zh-tw/v1/Git-%E5%9F%BA%E7%A4%8E-%E6%A8%99%E7%B1%A4

* How to tag an older commit in Git?

** REF: https://stackoverflow.com/questions/4404172/how-to-tag-an-older-commit-in-git