How to cancel a merge made into master branch

Question

I'm in this situation where I accidentally merged a branch into master.

Now, I want the master branch to get back to its previous state. I used git reset --hard HEAD^ but when I want to push I get this error:

Updates were rejected because the tip of your current branch is behind its remote counterpart

Is there any way I can fix this?

Answer 1

As I understand, you are currently working on the master branch and simply want to reset it to be exactly like its remote counterpart (i.e., discarding your changes). The simplest way to do this is:

$ git fetch
$ git reset --hard origin/master

If you've already pushed the merge that you made, you will have to do then have to do a force push. Be careful, however, since that will wipe out any changes that others had potentially made to master in the meantime.

$ git reset --hard <hash of commit that is the earlier version of master to which you want to revert, as shown in the merge commit that you made>
$ git push -f

Answer 2

You have several options:

1. delete the local branch and check it out again:

   # checkout temp branch
   git checkout - b tempBranch
   
   # delete the current branch
   git branch -D master
   
   # checkout the old branch
   git fetch --all --prune
   git checkout master
   

2. use the git reflog

git reflog

You can always use the reflog as well.
git reflog will display any change which updated the HEAD and checking out the desired reflog entry will set the HEAD back to this commit.

Every time the HEAD is modified there will be a new entry in the reflog

git reflog
git checkout HEAD@{...}

This will get you back to your desired commit

This will put you in a detached head and you will have to checkout new branch and follow the previous step as described in step #1.

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