Simplify rebasing in stacked branches using updateRefs

Working with Stacked PRs

Whether you are a developer at a small startup or a large enterprise, we all use pull requests to add features. Ideally, we would like to raise small PRs that are easier to review. Smaller PRs are easier for teammates to review and approve, especially if your team is using feature flags or multiple feature branches.

For a single feature, you might raise multiple PRs sequentially, like this:

master -> ..c..c.. (feature A)
master -> ..c..c.. (feature A) -> ..c..c.. (feature B)
master -> ..c..c.. (feature A) -> ..c..c.. (feature B) -> ..c.. (feature C)

The problems

Whenever I push code to GitHub, there are two main sources of anxiety for me:

1. Will all the CI tests pass?
2. Will I get review comments?

The second one causes even more mental stress, especially when I have stacked branches on top of the current branch. If the PR takes a long time to review, merge conflicts can occur, and now we have to resolve the same conflicts in multiple feature branches.

I’ve been in situations where a teammate and I were working on similar features, and the pain of resolving conflicts and rebasing stacked branches is hard to describe in words.

The Solution

After struggling with this for a while, I found a solution that fits perfectly for my use case: rebase.updateRefs.

When enabled, updateRefs keeps track of branch heads for stacked branches. This means that when I add fixup commits or resolve merge conflicts on the latest branch, these changes are automatically reflected in dependent branches. No more manually rebasing each branch one by one!

Sounds cool, right? Let’s see how we can use updateRefs

git config --global rebase.updateRefs true

Example we have three feature branches feat-a,feat-b and feat-c as follows.

> git log --oneline
2f4abed (HEAD -> feat-c) feat_c: commit-1
2bed7d2 (feat-b) feat_b: commit-1
259b5c8 (feat-a) feat_a: commit-1
077ef7c feat_a: commit-1
391ca2e (master) init

Say now we raised three PRs and got some review comments that require us to add changes to feat-a. In the ordinary way, we would checkout the feat-a branch and make modifications there, then rebase the other two branches to include the latest commit we added.

But with updateRefs, we can make modifications by staying in the latest branch (feat-c). In feat-c branch make changes and create a fixup commit for second commit of the feat-a 8199983.

git add . && git commit --fixup=8199983

Now rebase the fixup commit with master or the parent of feat-a. This is to include all the commits of feat-a onwards in the interactive rebase. So that we can squash or correcty place the fixup commit to it’s target.

git rebase --interactive --autostash master

Move the fixup commit to feat-a commit - 2

pick 077ef7c # feat_a: commit-1
pick 8199983 # feat_a: commit-2
pick f76e2a9 # fixup! feat_a: commit-2 # <---------- TO MOVED HERE
update-ref refs/heads/feat-a

pick cd066e7 # feat_b: commit-1
update-ref refs/heads/feat-b

pick ba57a88 # feat_c: commit-1
pick f76e2a9 # fixup! feat_a: commit-2 # <---------- FROM HERE

That’s it! Git will now automatically rebase the refs in the feat-a and feat-b branches:

Successfully rebased and updated refs/heads/feat-c.
Updated the following refs with --update-refs:
	refs/heads/feat-a
	refs/heads/feat-b

NOTE:

This will update the commit history of feat-b and feat-c so you have to force push the changes to Github.

History