How to unmerge a Git merge?

Question

I accidentally did a git pull origin master from dev, and master got merged into dev. Is it possible to unmerge?

I've already seen different solutions, i tried this one from both dev and master : git revert -m 1 <commit> (once each) But i got : Everything is up-to-date, each time

Answer 1

If it's a history merge. First to find the merge commit id using git log like this:

 git log --after="2022-09-29 00:00:00" --before="2022-09-30 23:00:00"

This will show the log in 2022-09-29 (suppose the merge happened in 2022-09-29)

Then find the commit id, and run:

git revert -m 1 <commit id>

Answer 2

If the merge has been accepted accidentally by git merge --continue or if the changes are auto committed when git pull <branch>, then we can revert or undo the very recent merge by executing

git reset --merge HEAD~1

This command reverts our repository to the last commit. HEAD refers to the current state of your repository; HEAD~1 is the last commit in your repository.

Answer 3

You can reset your branch to the state it was in just before the merge if you find the commit it was on then.

One way is to use git reflog, it will list all the HEADs you've had. I find that git reflog --relative-date is very useful as it shows how long ago each change happened.

Once you find that commit just do a git reset --hard <commit id> and your branch will be as it was before.

If you have SourceTree, you can look up the <commit id> there if git reflog is too overwhelming.

Answer 4

git revert -m allows to un-merge still keeping the history of both merge and un-do operation. Might be good for documenting probably.

Answer 5

If you haven't committed the merge, then use:

git merge --abort