git: I accidentally merged feature branch into master instead of develop

Question

I'm using git and working with master/develop/feature branches.

The master only had the README file. And, unfortunately, I accidentally merged the feature branch I was working into the master instead the develop branch. And also removed the feature branch.

I know little about git and I'm confused about what to do. But I think the right thing is to merge the changes on the feature branch (already removed) into develop and revert the merge into the master. But how to do that if I already removed the feature branch?

Answer 1

Note that I'm assuming here that you haven't pushed the results of the merge. If you have, this still can work, but would require a "force push" which in turn impacts everyone else using the repo (see "recovering from upstream rebase" in the git rebase docs; as that's essentially the situation it would create). But if you haven't, you don't need to worry about any of that. So:

First thing is to recreate the feature branch. I'm assuming it only ever existed locally. (If it had been pushed before the merge, you might be able to recover it from the remote; but either way the approach below will work.) So

git checkout master
git checkout -b feature
git reset --hard HEAD^2

Now the feature branch is restored to the merge commit's "second parent" - which should be where it was before the merge.

Next you need to remove the merge from master.

git checkout master
git reset --hard HEAD^

And that's it; you're ready to merge the feature into the development branch.