git reset hard,mixed,soft
首先，我们得了解git reset命令的形式之一：
git reset [
此命令的作用是恢复HEAD分支到
此外，mode还有两个值：–soft和–hard。
–soft不会改动(touch) index file和working tree，但是会撤销head到commit之间的all history，这是三个模式所共有的作用。
$ git status
On branch main
Changes not staged for commit:
(use "git add ..." to update what will be committed)
(use "git restore ..." to discard changes in working directory)
modified: README.md
no changes added to commit (use "git add" and/or "git commit -a")
$ git add README.md
$ git status
On branch main
Changes to be committed:
(use "git restore --staged ..." to unstage)
modified: README.md
$ git log --graph --oneline
\* 0a071ac (HEAD -> main) A
\* 0c888f4 Initial Commit
$ git reset --soft 0c888f4
$ git status
On branch main
Changes to be committed:
(use "git restore --staged ..." to unstage)
modified: README.md
$ git log --graph --oneline
\* 0c888f4 (HEAD -> main) Initial Commit
可以观察到commit A的committed changes都reset为staged changes to be committed。原本已经stage等待commit的changes不会被reset。HEAD指向
–mixed在–soft的基础上，进一步reset，它会恢复index到
$ git reset 0c888f4
Unstaged changes after reset:
M README.md
git reset会报告影响到的changes。
–hard会在–mixed的基础上恢复working tree的状态。被跟踪的changes会被丢弃。
Any untracked files or directories in the way of writing any tracked files are simply deleted.
Git文档中的这句话我不是太理解，通过询问ChatGPT，翻译为：任何阻碍跟踪文件的写入的未跟踪文件或目录将被删除。
下面是一个Stack Overflow对该疑问的解释代码例子：
There is a case in which git reset --hard has effects on untracked files.
$ touch a.txt
$ git add .
$ git commit -m'A'
$ echo hello >> a.txt
$ git add .
$ git commit -m'B'
$ git rm a.txt
$ echo world > a.txt
$ git status -s
The status output is
D a.txt
?? a.txt
The a.txt in the index is removed and the one in the work tree is untracked.
$ cat a.txt
world
Reset in the mode of --hard,
$ git reset --hard
$ cat a.txt
hello
$ git status
On branch master
nothing to commit, working tree clean
The untracked a.txt in the work tree is deleted. But we could also say it’s been overwritten with the tracked a.txt in HEAD.