1、fatal: cannot lock ref 'HEAD'：解决方法重新创建Head
echo ref: refs/heads/master >.git/HEAD
2、Updates were rejected because the tip of your current branch is behind
git fetch origin master
git commit
git merge origin/master
git push
3、master -> master (non-fast-forward)
可以通过如下命令进行代码合并【注：pull=fetch+merge]
git pull --rebase origin master
此时再执行语句 git push -u origin master即可完成代码上传到github
http://jingyan.baidu.com/article/f3e34a12a25bc8f5ea65354a.html
http://www.jianshu.com/p/835e0a48c825
