大话git中的撤销操作

下面以现实场景作为情境。

基础知识，理解git中的几个区域

本地代码已经add，未commit

修改本地工作目录中的readme.md,添加文字"第一次修改"

然后查看下状态

➜  experimentation git:(master) ✗ git status
On branch master
Your branch is up-to-date with 'origin/master'.
Changes not staged for commit:
  (use "git add <file>..." to update what will be committed)
  (use "git checkout -- <file>..." to discard changes in working directory)

        modified:   README.md

no changes added to commit (use "git add" and/or "git commit -a")

进行Add操作,并查看状态

➜  experimentation git:(master) ✗ git add README.md
➜  experimentation git:(master) ✗ git status
On branch master
Your branch is up-to-date with 'origin/master'.
Changes to be committed:
  (use "git reset HEAD <file>..." to unstage)

        modified:   README.md

➜  experimentation git:(master) ✗

这时候，变动进入了缓存区(Index)

但是我们突然发现我们改动错了，其实我是想改动experimentation.txt文件。

方法一：我们当然可以再次修改experimentation和readme文件（删除readme中的修改，给experimentation中添加“第一次修改”），然后再Add

方法二：我们想的可能是撤回之前的add操作，然后给experimentation中添加“第一次修改”，然后再次Add,那这样的话，我们如何操作呢？

• 撤销某个add文件:git reset HEAD <filename>

• 撤销全部add文件:git reset HEAD .

➜  experimentation git:(master) ✗ git reset HEAD README.md
Unstaged changes after reset:
M       README.md
➜  experimentation git:(master) ✗ git status
On branch master
Your branch is up-to-date with 'origin/master'.
Changes not staged for commit:
  (use "git add <file>..." to update what will be committed)
  (use "git checkout -- <file>..." to discard changes in working directory)

        modified:   README.md

no changes added to commit (use "git add" and/or "git commit -a")

Tip git log与git reflog的区别
git reflog 可以查看所有分支的所有操作记录（包括commit,reset的操作,已经被删除的commit记录)
git log不能察看已经删除的commit记录

本地代码已经add，已commit

---

将本地代码多commit几次,再来看下我们的提交log

• 方法一(推荐)：执行git revert <commitId>

撤回到指定的版本，包括文件和状态。

• 方法二：执行git reset <commitId>

➜  experimentation git:(master) git reset 2a6c701
Unstaged changes after reset:
M       experimentation.txt
➜  experimentation git:(master) ✗ git status
On branch master
Your branch and 'origin/master' have diverged,
and have 4 and 6 different commits each, respectively.
  (use "git pull" to merge the remote branch into yours)
Changes not staged for commit:
  (use "git add <file>..." to update what will be committed)
  (use "git checkout -- <file>..." to discard changes in working directory)

        modified:   experimentation.txt

no changes added to commit (use "git add" and/or "git commit -a")

回退至指定的版本，区别如下

Tip git revert与git reset的区别
git reset是直接删除指定的commit之前的所有commit(这是不安全的，特别是push后)，把HEAD向后移动。
git revert是一次新的commit，HEAD继续前进，与普通的commit一样。