Git Undo Merge: How to Revert the Last Merge Commit in Git

Introduction to Undoing a Merge in Git

Merging branches is a common operation in Git, allowing you to combine the changes from one branch into another. However, there may be situations where you need to undo a merge and revert the repository back to the state before the merge occurred. In this article, we will explore different methods to undo a merge in Git and revert the last merge commit. Whether you merged branches by mistake or need to backtrack, we’ve got you covered.

Understanding Merge Commits

Before we dive into undoing a merge, it’s essential to understand merge commits in Git. When you merge two branches, Git creates a new commit called a merge commit. This commit represents the combination of changes from both branches. The merge commit has two parent commits, one from each branch.

Reverting a Merge with Git Revert

One way to undo a merge is by using the git revert command. The git revert command creates a new commit that undoes the changes introduced by a previous commit. Here’s how you can revert the last merge commit:

1. Identify the Merge Commit: Use the following command to view the commit history and identify the hash of the merge commit:

git log

1. Revert the Merge Commit: Run the following command, replacing <merge-commit-hash> with the hash of the merge commit:

git revert -m 1 <merge-commit-hash>

The -m 1 option tells Git to revert to the first parent of the merge commit, effectively undoing the changes introduced by the merge.

Reverting a Merge with Git Reset

Another approach to undo a merge is by using the git reset command. Unlike git revert, which creates a new commit to undo changes, git reset modifies the commit history by moving the branch pointer to a previous commit. Here’s how you can use git reset to revert the last merge commit:

1. Identify the Merge Commit: Use the following command to view the commit history and identify the hash of the merge commit:

git log

1. Revert the Merge Commit: Run the following command, replacing <merge-commit-hash> with the hash of the merge commit:

git reset --hard <merge-commit-hash>

The --hard option resets both the branch pointer and the working directory to the state of the specified commit, effectively removing the merge commit and discarding all changes introduced by it.

Caution: Rewriting History

It’s important to note that both git revert and git reset modify the commit history. If you have already pushed the merge commit to a shared repository, be cautious when using these commands, as they can create conflicts and disrupt the work of other team members. It’s generally recommended to communicate with your team and plan the undoing of a merge collaboratively.

Recovering Lost Commits

When you undo a merge commit, you might lose the commits from the merged branch. If you want to recover these lost commits, you can use the git reflog command to find the commit hash of the commit you want to restore. Once you have the commit hash, you can create a new branch or cherry-pick the commit to reintroduce the changes.

Conclusion

Undoing a merge in Git allows you to revert the repository back to the state before the merge occurred. By using the git revert or git reset command, you can effectively remove the merge commit and undo the changes introduced by it. However, it