PR description after a rebase — re-summarizing
You've just finished a complex feature, crafted a beautiful pull request description, and are ready for review. Then, the inevitable happens: main has moved on. Maybe a critical bug fix landed, or another feature that impacts yours. So, you git pull origin main and then git rebase main. Or perhaps you decide your commit history is a bit messy and run git rebase -i to squash some commits.
Suddenly, that meticulously written PR description might be outdated, incomplete, or even outright misleading. The summary no longer perfectly reflects the changes, the test plan misses new edge cases, and the risk assessment is off. This is a common, frustrating reality for many engineers.
Why Rebase? (And why it's painful for PR descriptions)
Rebasing is a powerful git operation that allows you to rewrite your branch's commit history. It's an indispensable tool for maintaining a clean, linear project history, making merges easier, and improving code readability.
You might rebase for several reasons:
- To incorporate upstream changes: By rebasing your feature branch onto
main(or your target branch), you apply your changes on top of the latest upstream commits. This avoids merge commits, resulting in a linear history. - To clean up your commit history: An interactive rebase (
git rebase -i) lets you squash multiple "work-in-progress" commits into a single, logical commit, reorder commits, edit commit messages, or even split a commit. This makes your branch's history much easier to read and understand. - To fix an earlier commit: If you discover a bug or a typo in an older commit within your branch,
rebase -iallows you to go back andeditthat specific commit, then reapply subsequent commits on top.
While these benefits are significant, they come with a catch: rewriting history fundamentally changes the set of commits in your branch and, crucially, the overall diff between your branch and the target branch. Since pull request descriptions are often derived from these changes, they can quickly become stale or inaccurate after a rebase.
The Manual Grind: What Engineers Do Now
When your PR description becomes stale after a rebase, what do you usually do?
- Manual update: You open the PR description, scroll through your
git log --onelineto see what changed, and then manually edit the summary, test plan, and risk sections. This is tedious and prone to human error, especially after a complex rebase. git diffarchaeology: You might rungit diff main...HEADto see the actual changes that will be merged. Then, you try to mentally (or physically) cross-reference this with your existing description.- "Good enough" mentality: Often, in the rush to get code reviewed, engineers might skip updating the description entirely, hoping reviewers will figure it out from the code. This leads to longer review cycles and potential misunderstandings.
This manual process is a time sink and a common source of friction in the development workflow.
How Rebase Changes Your Diff (and therefore your PR)
Understanding how a rebase alters your branch's diff is key to grasping why PR descriptions need updating.