git submodule
https://qiita.com/sotarok/items/0d525e568a6088f6f6bb
https://qiita.com/kinpira/items/3309eb2e5a9a422199e9
https://www.d-wood.com/blog/2014/05/22_6257.html
http://vdeep.net/git-submodule
git subtree
との違い
git submoduleとsubtreeの違い
]
/miyamonz/git submoduleとsubtreeの違い
https://tech.guitarrapc.com/entry/2019/03/16/065700