【报错】Git: ! [rejected] master -> master (non-fast-forward)

原因：有代码没有add  commit
操作：
git fetch origin
git merge origin/master
git status
git add .
git status
git commit -m "add file"
git status
git push origin master

参考于：https://blog.csdn.net/sunnypotter/article/details/18957109