How to undo commit files by git

There are three ways to undo the Git commit file: the git reset command: move the HEAD pointer to the previous commit and undo the most recent commit; the git revert command: create a new commit to undo the previous commit modification, retain the integrity of the commit history; the git checkout command: restore the state of a single file to the previous commit.

How to undo commit files in Git? This question is awesome!

Many newbies, even some veterans, will find problems after Git's commit: they submitted files that should not be submitted, or submitted incorrect code. Don't panic, the power of Git is that it can easily deal with this "regret medicine" scenario. In this article, I will take you into some insights into several ways to undo commit files and share some lessons I have learned over the years in Git combat.

First of all, we need to be clear: Git's commit is not irreversible. The key is that you understand how Git works and choose the right command.

Basics: Snapshots and pointers

You need to understand how Git manages your projects. It is not a simple file backup, but a series of snapshots (commits) to record the project status. Each commit is like a point in time, recording snapshots of all files at that time. The HEAD pointer points to the latest commit of the current branch. Once you understand this, you will be able to better understand the subsequent operations.

Core: Several ways to undo commit

1. git reset command: time goes back

This is the most common method, which can move the HEAD pointer to the previous commit, thus undoing the most recent commit. But be aware that this is just moving the pointer, and the file changes are not really gone from your local repository.

For example: you submitted the wrong file and want to revoke the commit, you can do this:

 <code class="bash">git reset --soft HEAD^ # 撤销上一个commit，修改保留在工作区git reset --mixed HEAD^ # 撤销上一个commit，修改保留在暂存区（默认） git reset --hard HEAD^ # 撤销上一个commit，修改全部丢弃</code>

HEAD^ refers to the previous commit, HEAD~2 refers to the previous commit, and so on. The three options --soft , --mixed , and --hard determine the handling method of modification after revoking commit. --hard is the most thorough, but the risk is the greatest, please use it with caution! I personally usually use --mixed so that I can check the modifications and decide whether to keep them.

2. git revert command: elegantly undo

git reset is rougher, while git revert is more elegant. It creates a new commit to undo the previous commit modification. This means that your commit history will remain intact, just an additional undo commit.

 <code class="bash">git revert HEAD</code>

This line of command will create a new commit to undo the previous commit. Compared to git reset --hard , it is safer and more in line with Git's workflow. This approach is highly recommended, especially in multi-person projects.

3. git checkout command: restore a single file

If you just want to undo the commit of a specific file, not the entire commit, you can use the git checkout command:

 <code class="bash">git checkout HEAD^ -- path/to/file</code>

This line of command will restore path/to/file file to the previous commit state. This command is very convenient and can accurately undo the modification of a single file.

Trapped and sharing of experience

• git reset --hard 's risk: Always remember that git reset --hard is a dangerous operation. It will permanently delete the commit modifications you undo, unless you have backed up those modifications. Don't use this command unless you're very sure.
• Remote Repository Synchronization: If you have pushed the wrong commit to the remote repository, you need to be careful. git push --force can force overwrite remote repositories, but this can cause trouble for collaborators, avoid it unless you are very sure that doing so will not affect other people's work. A better approach is to use git revert to create a new commit to undo the wrong commit and then push it to the remote repository.
• Branch strategy: Developing good branch management habits can effectively reduce the occurrence of such problems. Before making important changes, create a new branch so that you can easily switch back to the main branch even if the wrong code is submitted.

All in all, which method to choose depends on your specific situation. git revert is usually the safest option, while git reset is more flexible but requires careful operation. Remember, understanding how Git works is key, which allows you to make smarter choices when you encounter problems. I wish you a smooth Git trip!

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