How to undo a merge on Bitbucket?

2 min read 07-10-2024

Undoing a Merge on Bitbucket: A Step-by-Step Guide

Merging branches in Git is a powerful way to combine changes from different development streams. But what if you accidentally merge the wrong branch or realize the changes you merged in are causing problems? Fortunately, Bitbucket provides a mechanism to undo a merge, giving you the flexibility to correct mistakes and maintain a clean repository history.

Understanding the Problem: Unwinding a Merge

Imagine you're working on a feature branch and need to integrate it with the main development branch. However, you accidentally merge your feature branch into the wrong branch, causing unexpected issues. You need to reverse this merge operation and restore your repository to its previous state.

The Original Code: A Before and After Scenario

Let's assume you have two branches: main and feature-branch. You accidentally merge feature-branch into main when you intended to merge it into another branch called development.

# Before the mistake:
git branch -a
  * main
    feature-branch
    development

# After the mistake:
git checkout main
git merge feature-branch

Now your main branch contains the changes from feature-branch, and you need to undo this merge.

Unwinding the Merge with Bitbucket: A Practical Guide

Here's how to undo a merge on Bitbucket:

Identify the commit: Find the merge commit you want to undo. You can do this by looking at the commit history in Bitbucket or by using git log in your local repository.
Create a new branch: Create a new branch from the commit before the merge you want to undo. This will give you a clean slate to work with.
Reset to the desired state: Use git reset --hard to reset your new branch to the commit before the merge.
Push the changes: Push your new branch to Bitbucket.

Example:

# Create a new branch based on the commit before the merge:
git checkout -b undo-merge main~1 

# Reset to the commit before the merge:
git reset --hard HEAD~1

# Push your changes to Bitbucket:
git push origin undo-merge

Create a pull request: Create a pull request from your undo-merge branch to the branch you originally wanted to merge feature-branch into (in this case, development). This will allow you to review the changes before merging them into your target branch.
Merge the changes: Once you've reviewed and approved the changes, merge the pull request. This will undo the accidental merge and integrate your feature-branch into the correct branch.

Additional Tips and Considerations

Backup: Before making any changes, ensure you have a backup of your repository.
Revert vs. Reset: git revert creates a new commit that undoes the changes introduced by a previous commit. git reset rewrites the history, which can be useful for undoing a merge but can lead to conflicts if others have already worked on the branch.
Collaborators: If others have already worked on the branch you accidentally merged into, you'll need to coordinate with them to resolve potential conflicts.

Conclusion

Undoing a merge on Bitbucket is a straightforward process that allows you to recover from mistakes and maintain a clean development workflow. By following these steps, you can ensure your repository remains in a desired state and your project stays on track.