How to Git rebase onto another branch

Understanding git rebase

Rebasing is a process in Git that involves moving or combining a sequence of commits to a new base commit. Rebase is useful for integrating changes from one branch into another without creating a merge commit. It's particularly advantageous for cleaning up your commit history before merging a feature branch into the main branch.

Key concepts of git rebase

• Linear history: Rebasing helps maintain a linear project history, which can simplify both navigation and troubleshooting.
• Avoiding redundant merges: By rebasing, you can avoid unnecessary merge commits, keeping your project history clean and readable.

Steps to Rebase onto Another Branch

Here’s how to rebase one branch onto another, effectively changing the base of your feature branch to incorporate updates from the mainline or another branch.

1. Fetching the latest changes

Always start by fetching the latest changes from your repository to ensure that your local branches are up-to-date.

git fetch origin

This command will update your remote-tracking branches.

2. Checking out the feature branch

Switch to the branch you want to rebase. This is typically a feature branch that you want to update with changes from another branch.

git checkout feature-branch

3. Rebasing onto another branch

Now, perform the rebase operation to change the base of your feature branch to another branch, such as main or develop. The following command rebases the current branch onto the main branch:

git rebase main

Alternatively, if you want to specify that the rebase should start from a particular commit on your feature branch and move onto a different branch, you can use:

git rebase --onto main start-point feature-branch

In this command, start-point refers to the commit on your feature branch where you want to start the rebase.

4. Resolving conflicts

During rebase, conflicts may occur. Git will stop at the first conflicted commit and allow you to resolve conflicts. After resolving each conflict, you need to stage the changes with git add and then continue the rebase:

git rebase --continue

If at any point you need to abort the rebase process, you can do so with:

git rebase --abort

For a more detailed walkthrough on how to resolve these issues see this guide on Git merge conflicts.

5. Completing the rebase

After resolving all conflicts and completing the rebase, your branch history will have been rewritten to start from the latest commit of the main branch.

6. Pushing the rebased branch

If your branch has been previously pushed and you've changed its history by rebasing, you'll need to force-push to update the remote branch:

git push origin feature-branch --force

When you rebase a branch in Git, you essentially rewrite its commit history, potentially altering the commits' SHA-1 hashes and their relationships. If you attempt to push the rebased branch to the remote repository without force-pushing, Git will reject the push operation because it recognizes that the commit history has diverged from the remote branch's history.

To overcome this, you use the --force flag with the git push command, indicating that you are aware of the history changes and intentionally want to overwrite the remote branch with the rebased version. By force-pushing, you update the remote branch to reflect the new commit history of your local branch.

However, it's crucial to exercise caution when force-pushing, especially in collaborative environments, as it can potentially disrupt other developers' work if they have based their changes on the previous version of the branch. It's generally recommended to communicate with your team before force-pushing to ensure that everyone is aware of the changes and can adjust their work accordingly.

For further reading on rebasing see the official Git documentation.