https://learnvimscriptthehardway.stevelosh.com/chapters/42.html
git clone --recursive [email protected]:craigmac/vimfiles ~/.vim
git submodule add <url>
cd ~/.vim/pack/third-part/opt/vim-foo
git pull origin master
git submodule foreach git pull origin master
cd ~/.vim
git submodule deinit pack/third-party/opt/vim-foo
git rm -rf pack/third-party/opt/vim-foo
rm -r .git/modules/pack/opt/vim-foo