How do I undo a Git merge?

I accidentally merged the wrong branch in Git. How can I undo that merge?

You can undo a Git merge by using the command git reset --hard HEAD~1. This will reset your branch to the state before the merge.

What if I already pushed the merge to the remote repository?

If you've pushed the merge, you'll need to use git revert -m 1 <merge_commit_hash> to create a new commit that undoes the changes.

Can you explain what -m 1 means in that command?

The -m 1 option specifies the parent number to use for the revert. In a merge commit, there are two parents, and 1 refers to the first parent.

Is there a way to recover the changes I made in the merge?

Yes, you can create a new branch from the merge commit before reverting, allowing you to keep those changes if needed.