通过 git submodule add命令引入子模块，命令如下：
git submodule add http://xxx.xxx.xxx/xxx.git ./sub/dir
在子模块中修改和提交代码，直接提交至子模块自身git
通过 git rm 删除子模块，删除命令如下
git rm -f submodule_name #同时删除本地文件 或 git rm --cached submodule_name #保留本地文件
第一次使用时，错误的将本地代码add至当前repo （git submodule add ./local/code/dir ./sub/dir）导致无法push子模块，提示如下错误：
remote: error: refusing to update checked out branch: refs/heads/master remote: error: By default, updating the current branch in a non-bare repository remote: error: is denied, because it will make the index and work tree inconsistent remote: error: with what you pushed, and will require 'git reset --hard' to match remote: error: the work tree to HEAD. remote: error: remote: error: You can set 'receive.denyCurrentBranch' configuration variable t remote: error: 'ignore' or 'warn' in the remote repository to allow pushing int remote: error: its current branch; however, this is not recommended unless you remote: error: arranged to update its work tree to match what you pushed in som remote: error: other way. remote: error: remote: error: To squelch this message and still keep the default behaviour, se remote: error: 'receive.denyCurrentBranch' configuration variable to 'refuse'.
重新add 远程git路径得以解决
参考链接：
http://a.ghuser.io/git-pushing-a-new-submodule/
https://git-scm.com/docs/git-submodule
https://git-scm.com/book/zh/v2/Git-%E5%B7%A5%E5%85%B7-%E5%AD%90%E6%A8%A1%E5%9D%97
https://stackoverflow.com/questions/6414675/git-pushing-submodule