Commits and Pull Requests (diffs) are very similar, but they’re not the same thing. The basic difference is that git commits are local (ish) and PRs/Diffs are public. And there’s a lot of value in understanding the difference between your private and public record of changes. But what’s that got to do with tick-tock?
One way they’re related is refactoring. There are lots of reasons to refactor code, but they mostly come down to not knowing what you didn’t know. Yes, sometimes you just get the design wrong with full knowledge, but much more often either you didn't know what you were going to need at first, or the requirements changed after the fact. Regardless of the reason, there will come a time when you need to refactor to make a business (functional) change.
Another way to know if you should have more than one PR is to think about your PR message. The subject should be short, imperative, and have one goal. If your subject looks like conjunction junction you should probably split the PR.
And that’s where tick-tock comes in. You could do them both at once. A single moment in time that changes everything. But is that really the best way?
Maybe, but probably not. A better way would be to refactor first (tick), then make the business change (tock) as two completely separate PRs. There are lots of good reasons. Here’s some of the big ones:
- Your automated tests ensure that nothing changed with the refactor. You shouldn’t need to touch most of your tests. They should be testing the functionality, not the structure of your code. Of course if the refactor includes an API change then you’ll need to do some modifications, but the changes should be simple.
- You spread knowledge of the refactor by itself. If code is truth and documentation is context, the refactor speaks for itself and others are aware of it and can take advantage of it
- It’s easier for the reviewer. Each PR has one goal, so there’s less cognitive load when trying to understand it. The refactor should have no functional changes, and the functional change should only make the change