Undoing a Git Revert
Git’s revert command is a powerful tool for undoing changes without altering the project’s history. However, sometimes you might find yourself needing to undo a revert – effectively reapplying the changes you initially reverted. This tutorial explains how to achieve this safely and effectively.
Understanding the Scenario
Let’s say you have a commit (let’s call it commitA) that you made, and you later decided to undo it using git revert commitA. This creates a new commit (let’s call it commitB) that reverses the changes introduced by commitA. Now, you’ve realized you didn’t want to revert commitA in the first place. You want to restore the original changes. The key is to do this without rewriting history, which can cause problems for collaborators.
Methods for Undoing a Revert
There are several ways to undo a revert, each with its own advantages:
1. Reverting the Revert (Recommended)
The most straightforward and often preferred method is to revert the revert commit itself. Since a revert is just a regular commit, you can treat it like any other and revert it.
git revert <commit-hash-of-revert-commit>
Replace <commit-hash-of-revert-commit> with the SHA-1 hash of the commit that performed the revert (e.g., git revert ghijkl). This creates a new commit that reapplies the changes originally introduced by commitA.
Why this is good: This method preserves a clear audit trail. You have a record of the original commit, the revert, and the undoing of the revert. It’s easy to understand the sequence of events by examining the commit history.
2. Cherry-Picking the Original Commit
Another effective method is to use git cherry-pick. This command allows you to select a specific commit and apply its changes to your current branch.
git cherry-pick <commit-hash-of-original-commit>
Replace <commit-hash-of-original-commit> with the SHA-1 hash of the original commit (e.g., git cherry-pick abcdef). This effectively reapplies the changes from commitA to your current branch.
When to use this: If you only need the changes from the original commit and don’t necessarily care about preserving the exact commit history, cherry-picking is a good option.
3. Resetting (Use with Caution – Local Only!)
If the revert commit has not been pushed to a remote repository, you can use git reset --hard HEAD^. This will effectively remove the revert commit from your local history. This method rewrites history and should only be used on local branches that haven’t been shared.
git reset --hard HEAD^
Important: Never use git reset on shared branches, as it can cause significant problems for your collaborators.
Finding Commit Hashes
You can find the commit hashes of both the original commit and the revert commit using the git log command:
git log --oneline
This displays a concise history of your commits, including their commit hashes and commit messages. You can also use more specific filters with git log to narrow down the results. For example, git log --author="Your Name" will show commits authored by you.
Best Practices
- Always prefer creating new commits over rewriting history. This minimizes the risk of disrupting your collaborators and ensures a clean, auditable history.
- Use clear and descriptive commit messages. This makes it easier to understand the purpose of each commit and track changes over time.
- If you’re unsure, err on the side of caution. Before making any changes to your Git history, make sure you understand the potential consequences and have a backup of your work.
By following these guidelines, you can confidently undo Git reverts and maintain a clean and reliable project history.