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How to undo local commits

There are two ways to undo a commit:

  • By telling Git to create a new commit which exactly undoes the changes of a previous commit (e.g. deleting lines of code instead of adding them).
  • By telling Git to get rid of a commit entirely.

These are known as git revert and git reset.

git revert​

This tells Git to create a new commit which exactly undoes the changes of a previous commit.

This is a safe undo. After all, if you decide you didn't want to revert your commit after all, you can revert the revert.

In addition, when you start sharing your commits with other people, it's normal for contributors to add commits, but it is not normal for contributors to remove commits.

Therefore you should use git revert in either of the following cases:

  • You want the flexibility to bring back your changes later.
  • You are using a remote repository (more on that soon).

git reset​

This tells Git to get rid of a commit entirely.

This is not a safe undo. It is not possible to bring back your commit after it's been deleted.

If you're sharing your repository with others, they will have problems when you delete commits.

Therefore, you can use git reset when both of the following are true:

  • You are sure you never want the commit you're deleting again.
  • You are not sharing the repository with others.

I'd recommend using git revert almost every time!

How do you use them?​

First, you need to know which commit you want to undo. Usually it's the last commit you've made, but it can be one before that.

You need to find the commit hash: a unique identifying code that each commit has.

We can find it by using git log. In this example we've got two commits, and this would be the result:

git log

commit ae77aedd4cec3b0a6c130a2699dbb7003257033b (HEAD -> master)
Author: Jose Salvatierra <jose@tecladocode.com>
Date:   Mon Dec 16 12:23:26 2019 +0000

    Added changes to app.py to start the Flask app on Debug mode.

commit 0919fd47cae93ac2003b2865f8ffdd1b72e092d3
Author: Jose Salvatierra <jose@tecladocode.com>
Date:   Fri Dec 13 13:21:19 2019 +0000

    Load environment variables from dotenv file locally.

You can see that each commit has a long string of numbers and letters associated with it. That's the commit hash.

Next we can pass the first few characters of that to either git revert or git reset:

git revert ae77aedd

Simple as that!

A new commit is created that reverses the previous one.