1. 重新取回历史版本
git log
git checkout (这里写 上面查询出来 commit 后面的哈希值)
2. 此时使用git push会碰到如下问题：
$ git push
fatal: You are not currently on a branch.
To push the history leading to the current (detached HEAD)
state now, use
git push origin HEAD:<name-of-remote-branch>
解决方案：
git checkout -b temp 切换到一个临时的分支
git checkout master 再切换回主分支
git push