How And When To Use Git Reset

Most of us avoid dreaded git reset command — but actually it can be really useful, as long as you know how it works!

What does git reset do?

To put it simply, git reset will take your branch back to a certain point in the commit history, but there are 3 different levels to this:

• soft: Moves the head back to the commit specified but leaves all the updated files in the index and working directory —all of the files after the commit that you’ve moved to have been tracked (like doing git add) and are ready to be committed as a new commit.
• mixed: Moves the head and index back to the commit specified but leaves the files in the working directory — all of the files after the commit are in your working directory as untracked files. If you add them all now, you’ll be at the same stage as a soft reset above.
• hard: Moves the head, index and working directory back to the commit specified — all of the updated files after the commit specified are now *GONE*!!! (uncommitted files are unrecoverable at this point)

Why would you need this?

Here are a few examples so that you will have a better idea of when to use each. You should only ever do this on your own branch, or when you're sure no one has already pulled any of the commits that you will be removing.

Soft

Let’s say you have done a few tiny commits and you want them to all be put into 1 more descriptive commit.

A -> B -> C -> D

git reset — soft A

Your branch head is now pointing at A

git commit -m “my new merged commit”
git push origin branch --force-with-lease

We now have a new commit, E but it contains all of the files that were committed in B, C, D. Note: the force-with-lease flag is because otherwise git will complain that your local branch is behind the remote. (This is a safer version of force)

A->E

Mixed

You’ve just pushed a few commits, but you want to go back and remove a couple of files in a previous commit.

A->B->C

git reset --mixed A

Your branch head and index is pointing at A

git status

This will show that all of your changes in B and C are there, but are untracked

Now you are free to add the files that you wish to add into a new commit

git add <files> git commit -m "updated commit"
git push origin branch --force-with-lease

A->D

Your head is now at the new commit D, and any files that you’ve not staged will still be in your working tree, ready to add into another commit or to do what you want with.

Hard

When would you possibly want this? Usually when things have gone wrong because it’s VERY RISKY. I’ll talk you through a scenario where I’ve needed it.

I’ve been working on my own branch, testing out a feature and I’ve changed many files, but it’s been a fail and I want to go back a few commits and get rid of every change I’ve made since.

If I’ve not made any commits or pushed any commits. I can just reset back to commit A and my working directory is now clear, all of my updated files are gone from history.

git reset --hard A

If I’ve actually pushed these commits to my remote branch, then, before doing this, you need to make sure that no one is working from those commits because they will be orphaned. But if you know that it’s safe to do, then run the command above. The only difference here is that you will need to do a FORCED push afterwards to push the remote branch to that state, otherwise it will tell you that your local branch is behind.

git reset --hard A
git push origin branchname --force-with-lease

This will delete your commits from the remote branch history, so you can see it could be very dangerous.

I have used this to get me out of reverted merge commit hell recently. I did a pull request to merge a branch into another branch, it had merge conflicts and the conflicts were not resolved correctly, so I reverted the merge. This however meant I couldn’t do the pull request again because it saw no updates, so I tried to revert that and it ended up in a bit of a mess. I then used git reset --hard to take the branches back to before this situation and get rid of these ugly reverts in the history!

Hopefully now you will see that git reset is very powerful and can help you in some situations, used with care!

Originally posted on Medium