Undoing an Unpushed Git Merge

How can you undo an accidental merge in a local repository that has not yet been pushed to the remote?

The Solution

If the Merge Has Not Been Committed

If the merge has not been committed (i.e., git merge was run without the --commit flag and git commit has not been executed since the merge), you can abort the merge using:

git merge --abort

This command will stop the merge process and revert the working directory to the state before the merge began.

If the Merge Has Been Committed

If the merge has been committed, you can use git reset to undo the merge:

git reset --merge ORIG_HEAD

• git reset is used to return the current branch to a previous state.
• The --merge flag ensures that changes made to files by the merge are reverted, but it preserves changes that have not yet been included in any commit, preventing loss of uncommitted work.
• ORIG_HEAD refers to the state of the repository before the merge operation. This reference is created automatically when running commands like git merge to provide an easy way to undo them.

Force Pushing the Changes (If Required)

If you have accidentally pushed the merge to the remote repository and need to rewrite the remote history, you can force push the changes:

git push origin my-branch --force

Note: Use force push with caution as it rewrites the commit history on the remote repository, which can affect other collaborators working on the same branch.

Summary of Commands

• Abort an uncommitted merge:

  git merge --abort

• Undo a committed merge:

  git reset --merge ORIG_HEAD

• Force push to update the remote repository (if necessary):

  git push origin my-branch --force

By following these steps, you can effectively undo an accidental merge in a local Git repository, ensuring your repository is returned to its desired state.