Undoing Mistakes Safely: restore, amend, reset, revert and stash

Git is a safety net

The best thing about Git is not saving your work. It is that you can undo almost anything. That makes you braver: you can try a risky change, knowing you can get back.

The trick is knowing which tool fits which mistake. This lesson is a map. The questions to ask each time are: Where is the mistake? In my working folder, in the staging area, or in a commit? And has anyone else already got that commit?

Undo a change to a file: git restore

You changed a file and made a mess. You want it back the way it was at the last commit.

git restore notes.txt

Try it. The file below has been changed. Look with git diff, then restore it and check git status.

Unstage a file: git restore --staged

You ran git add . and staged something you did not mean to, perhaps a file with a password in it. Nothing is lost. You only change which things are in the waiting room.

git restore --staged passwords.txt

The file stays exactly as it was in your folder, but it is no longer going into the next commit. You will see this in the task below.

Fix the last commit: git commit --amend

You just committed, and then spotted a typo in the message, or realised you forgot to add a file. Instead of making a messy extra commit, replace the last one:

git add forgotten-file.txt
git commit --amend -m "Add the contact page with its style file"

Amend swaps the last commit for a new one. It is perfect for tidying up your own recent work. Do not amend a commit that you have already pushed for others to use, because it rewrites history they depend on.

Move back in history: git reset

git reset moves your branch back to an earlier commit. It has three modes, and the difference is what happens to your changes.

HEAD~1 means "one commit before the current one". The usual story: you committed too early. git reset --soft HEAD~1 undoes the commit but keeps all your work staged, so you can fix and recommit. Try it, and then look at git status and git log --oneline after each step.

Undo a shared commit safely: git revert

git revert does not erase anything. It makes a new commit that does the opposite of an earlier one. The history grows, and nothing is rewritten, which makes it safe even after you have pushed.

git revert HEAD              # undo the last commit
git revert a3f9c21           # undo a specific older commit

Git writes the message for you, such as Revert "Set all prices to zero". In the history, it reads honestly: something went wrong, and here is the commit that fixed it. This is how teams undo mistakes on shared branches.

Park your work: git stash

Imagine you are halfway through a change, with files half-edited and not ready to commit, and your manager says: "There is an urgent bug on the main branch. Fix it now." You cannot commit half-finished work, and you cannot switch branches with it in the way.

git stash puts your uncommitted changes in a drawer and gives you back a clean folder:

git stash              # put the changes away
git switch main        # (do the urgent work here)
git stash pop          # take them back out
git stash list         # see what is in the drawer

Try the stash cycle yourself.

Run git status (a change), git stash (clean again, and your edit is hidden), git status, and finally git stash pop to bring the edit back.

When something feels lost

Git rarely loses committed work. Even after a hard reset, the old commits usually still exist for a while, and git reflog lists every place your HEAD has been, so an expert can get them back. If you ever panic, stop, do not run more commands, and ask for help. Committed work is very hard to lose. Uncommitted work is the fragile kind, which is another reason to commit often.

A golden rule

Before any command that rewrites history (amend, reset), ask: "Has anyone else got these commits?" If the answer is yes, use revert.

Try it

First, undo a bad commit on a shared branch the safe way. The last commit set every price to zero by mistake.

Now fix a staging mistake. Two files were staged, and one of them has a password in it.

Optionally, practise the stash cycle for real.