Undoing Changes Safely

Introduction

Everyone makes mistakes in Git. The good news is that nearly all of them can be undone, if you pick the right tool. The key question is: where is the mistake? In your files, in the staging area, in a local commit, or in a commit you already shared?

The simple explanation

For private work you can rewrite history. For shared work, add a new commit that undoes the old one.

Mistake in your files (not committed)

Throw away changes to one file and go back to the last commit:

git restore notes.txt

This permanently discards your edits to that file, so be sure.

Mistake in the staging area

Unstage a file but keep your edits:

git restore --staged notes.txt

Mistake in the last commit

Forgot a file or made a typo in the message? Amend the last commit:

git add forgotten.txt
git commit --amend -m "Add notes and forgotten file"

Amending replaces the last commit with a new one. Do this only if you have not pushed it yet.

Undo a commit you already shared: revert

git revert makes a new commit that does the opposite of an earlier one. History stays intact, so it is safe on shared branches.

git revert a1b2c3d

Replace a1b2c3d with the commit's hash from git log --oneline.

Move back in history: reset

git reset moves the current branch to an earlier commit. It has three common modes:

HEAD~1 means "one commit before the current one". --hard can destroy uncommitted work, so use it carefully.

Reset rewrites history. Use it on local work only. If you reset commits that others already have, their history and yours diverge and it causes trouble.

Safety net: the reflog

Git remembers where your branch has been for a while. If you reset too far:

git reflog
git reset --hard HEAD@{2}

git reflog lists recent positions of HEAD. Find the one you want and reset back to it. It works only on your own computer and for a limited time.

Try it yourself

In a practice repository, make two commits. Use git revert on the last one and look at git log --oneline. Then use git reset --soft HEAD~1 on a different practice commit and notice your changes are still staged.

Summary

• restore fixes files and the staging area, and commit --amend fixes the last commit.
• revert safely undoes shared commits by adding a new one.
• reset moves a branch and rewrites history, so use it only on private work, with reflog as a safety net.