How to Use Git Rebase – Tutorial for Beginners

As developers, we know how crucial version control systems like Git are for collaborating on codebases and managing changes over time. While most of us are familiar with common Git commands like branch, commit, push and merge, fewer developers take full advantage of the power of git rebase. When used properly, rebasing can help keep your repository‘s history clean and linear, making it easier for others to understand the evolution of the project. In this tutorial, we‘ll dive deep into git rebase and learn how to incorporate this useful tool into our Git workflow.

Git Merge vs. Git Rebase

Before we talk about git rebase, let‘s make sure we understand how it differs from the more commonly used git merge. When you merge one branch into another, Git creates a new "merge commit" that ties together the histories of both branches, joining them to a single timeline. While merging is a straightforward way to integrate changes from multiple branches, it can result in a cluttered project history, especially if you‘re merging frequently.

In contrast, rebasing works by transferring the commits from your current branch and replaying them at the end of the branch you‘re rebasing onto. Instead of using a merge commit, rebasing re-writes the project history by creating new commits for each of the original branch‘s commits. In the process, unwanted history is eliminated, resulting in a perfectly linear project history.

When to Use Git Rebase

So when should you use git rebase instead of git merge? Here are some scenarios where rebasing is potentially a better choice:

1. Cleaning up local commit history before pushing to a shared branch or submitting a PR. Rebasing allows you to alter previous commits, squashing multiple "work in progress" commits into a single well-described one.

2. Pulling in upstream changes to your feature branch. If the branch you based your work on advanced, rebasing allows integrating those changes while keeping your branch‘s history clean.

3. Resolving merge conflicts. When working on a long-lived feature branch, performing a rebase and resolving conflicts periodically reduces integration issues down the line.

On the other hand, it‘s better to stick to git merge when:

1. Pulling others‘ changes into your repository. Merging is non-destructive, whereas rebasing changes history, which could cause issues for others.

2. Integrating two branches that will continue to be developed independently and/or have widely divergent codebases. Excessive rebasing can be difficult to deal with and result in more conflicts.

Step-by-Step Guide to Git Rebase

Ready to try rebasing yourself? Follow these steps:

1. Make sure your working tree is clean by committing or stashing any changes.

2. Check out the branch you want to rebase onto. Typically this is the main development branch, e.g. main or develop. Use git checkout main to switch to it.

3. Pull the latest changes from the remote repository to ensure you have the most recent commits: git pull.

4. Check out the branch with your feature or bugfix: git checkout feature-branch.

5. Start the rebase with git rebase main. This will rewind your feature branch, pull in the latest changes from main, and then replay your commits one by one on top.

6. If Git encounters any conflicts during the rebase, it will pause and prompt you to resolve them. Make the necessary changes in your code, stage them with git add, and then continue the rebase with git rebase --continue.

7. Once the rebase is complete, your feature branch now has a nice linear history on top of the latest changes from main. Since the feature branch‘s history has changed, use git push --force-with-lease to force push the changes to your remote repository.

Interactive Rebasing

Git‘s interactive rebase tool is a powerful way to clean up your commit history. Running git rebase -i will open your text editor with a list of the commits about to be rebased:

pick 1fc6c95 Patch A
pick 6b2481b Patch B
pick dd1475d something I want to split
pick c619268 A fix for Patch B
pick fa39187 something to add to patch A
pick 4ca2acc i cant‘ typ goods
pick 7b36971 something to move before patch B

# Rebase 41a72e6..7b36971 onto 41a72e6
#
# Commands:
#  p, pick = use commit
#  e, edit = use commit, but stop for amending
#  s, squash = use commit, but meld into previous commit
#
# If you remove a line here THAT COMMIT WILL BE LOST.
# However, if you remove everything, the rebase will be aborted.
#

This allows you to:

• Re-order commits by changing the order of the lines
• Omit commits by deleting lines
• Squash commits by changing pick to squash (or s for short). This melds the commit into the one above.
• Split a single commit into multiple ones by changing pick to edit, committing the staged changes, and running git rebase --continue

Once your happy with the rebase plan, save and close the editor to complete the interactive rebase.

Resolving Rebase Conflicts

Just like merging, rebasing can result in conflicts if the same parts of a file were modified in the original and rebased branch. When this happens, Git pauses the rebase and prompts you to resolve the conflicts.

Git will mark the problematic areas in the affected files:

<<<<<<< HEAD 
Some code from main branch
=======
Some code from feature branch
>>>>>>> feature-branch

To resolve, edit the files to the desired state, removing the <<<<<<<, ======= and >>>>>>> lines. Use git add to stage the resolved files, and continue the rebase with git rebase --continue.

For help resolving merge conflicts, consider using a visual merge tool like git mergetool. Many IDEs also have built-in merge conflict resolution features.

When Not to Rebase

While rebasing is a handy tool, it‘s not always the appropriate choice. Avoid using git rebase in these situations:

1. On public branches that others are also working off of, like the main development branch. Rebasing effectively rewrites the project history, which could cause serious issues for others‘ branches.

2. On branches that have been used to create a tag or release. Tags and releases should represent a snapshot of your repository at a particular point in time. Rebasing would alter the commit history, making the release or tag invalid.

3. On large and/or long-running branches being worked on by multiple collaborators. Excessive rebasing, especially when dealing with many conflicts, can be complicated, time-consuming, and result in more issues than it solves.

Git Rebase Best Practices

To ensure you‘re using git rebase effectively and avoiding potential pitfalls, keep these best practices in mind:

1. Rebase your local changes before pushing them to the remote repository. This keeps your feature branch up to date with the latest changes and avoids integration issues.

2. Never rebase shared branches that others are also working on. Rebasing effectively rewrites history, which will cause issues for anyone else using that branch.

3. Communicate with your team before rebasing on a branch you‘re collaborating on together. Make sure everyone has pushed their latest changes and are aware of the rebase.

4. If you run into complex rebase conflicts, don‘t be afraid to abort and try a different approach. Use git rebase --abort to cancel the rebase entirely.

Conclusion

Git rebase is a powerful tool for keeping your repository‘s history clean and making it easier for others to understand the project‘s evolution. By replaying your feature branch‘s commits on top of the latest changes from the main development branch, rebasing results in a linear history free of unnecessary merge commits.

That said, rebasing isn‘t always the right choice. It‘s best used for cleaning up local commits before merging or pulling in upstream changes to a feature branch. Avoid rebasing on shared branches, or those used for releases or tags.

By understanding when and how to rebase, you can keep your Git history tidy, avoid integration headaches, and make your codebase more approachable for yourself and your team. Give git rebase a try in your next project – with a bit of practice, it‘ll soon become an indispensable part of your Git toolkit!