Posted by tomzorz 4 hours ago
For example, merging an entire stack is completely broken in many cases: https://github.com/github/gh-stack/discussions/212
You can merge one by one, but if you're using squash and merge, you need a re-approval for each PR in the stack if you require reviews. This makes you lose out on arguably the biggest gain of stacked PRs.
The command line tooling (gh stack) helps to make things slightly less manual, but you still need to be very aware of how git rebase works, the tooling just helps automate it across multiple branches. For example, just running the "gh stack rebase" commands that the UI suggests won't work if your local branches are not in sync with the remote ones, and the tooling won't point that out to you.
I do find the stack UI quite nice. It's quite minimal compared to standalone PRs, but it's enough to show the relationship between them.
(My comments all assume you already have a good reason to stack PRs. This tooling just help to make the workflow easier, it does not give any new capabilities)
There's an internal system we have called CPRMC (Create Pull Request Merge Commit) that is used to evaluate whether a PR is "ready" to merge. This covers everything from mergeability (checking for merge conflicts) to rule evaluations (ensuring that approvals match the potential commit that will be created by merge) and more.
This becomes particularly difficult when squash merging a stack of multiple PRs because we have to calculate a series of squashed commits, then associate those back to the rules/reviews. This is relatively easy for the first PR, but for the second PR onwards this gets more complicated because the ancestor commits are squashed and don't exist on the branch as-is. And I won't get into how much more complicated it gets for multi-parent situations lol.
It's something we need to fix and it's the top priority for the team. Our numbers show that 99% of stack merges go through successfully, but we need to get that much higher.
Thank you for being an early user in the preview and bearing with us while we work out these issues!
By the way could there be a way to disable that when doing integrations externally? It seems to be quite costly (which makes sense), and the pull/ refs kinda bloat the reflist.
I’m sure that external integration is not exactly beloved internally but there’s really just a small handful of big annoyances which would make it so much nicer and more comfortable.
Excited to release this more broadly so anyone can start stacking: https://gh.io/stacks
Would love to hear any feedback, especially with the UI and CLI. We've got a lot more updates to the PR experience in store!
Also happy to answer questions about the design decisions we made. There's a bunch happening behind the scenes, and it's one of the largest launches in GitHub history covering almost every service from Actions and protection rules to the CLI and mobile apps.
If you buy the idea that stacking produces better software, then this also has the opportunity to really help out quite a few people.
I think the bigger problem is that big AI PR's need a different way of reviewing. For example, the order in which the diff's are shown can make a big difference in how easy the commits are to read (e.g., function definition change first, then all call sites, then the tests).
Or maybe we should go to a system where diffs & comments are intertwined, a bit like how "Literate Programming" intertwines code and prose.
Literate diffs / literate pull requests... I haven't found anything like that yet.
For the people who work with stacked diffs (in phab/otherwise) this is exactly what they'd consider reviewing a well-curated set of commits one-by-one.
One distinction is that cognitively a unit of review (a PR, a diff) remains a single bound change. Comments are focused on that change and the PR does not grow with size of the feature
Another distinction is the ability to focus each part of the stack to a particular audience. One change may require review from an external team, another may be just your team mate, a third might be the consuming team. By focusing the stack to the different reviewers you can avoid ambiguity about "what a person is signing off on" in the stack.
aside: one thing that would be great for github reviews is the adoption of change ids such that comments persist across reviews with a rebase workflow.
> . By focusing the stack to the different reviewers you can avoid ambiguity about "what a person is signing off on" in the stack.
That can be easily done with comments. If the PR are orthogonal, they could have been split. And if they're not, I would really like to know how the part that I'm reviewing interacts with the rest of the changes.
Comments are ad-hoc and don't scale, relying on the author to interpret and adhere to the extent of the reviewers approval.
> And if they're not, I would really like to know how the part that I'm reviewing interacts with the rest of the changes.
you are free to look up, down, and around the stack; nobody is hiding the code from you. But in many cases this is just unnecessary.
I strongly believe that PR should be compared to the main branch, and not rely on unmerged code. Unless you merge everything together in one go. And in the latter case, everything should be reviewed together.
What I can see is that you can easily append commits to e.g. the first PR in a stack, which would insert them into the middle of sequence of commits.
This will require rebasing and fixing the subsequent PRs in a stack the same way you'd need to rebase and fix the subsequent commits in a mega-PR. But it makes the right thing easy (keeping all the commits to the foundation of the change together) rather than makin the wrong thing easy (appending fixup commits across the entire change in a random order so that the actual foundational change is lost).
Keeping all the foundational commits together also keeps all the discussion over the foundational change together.
You could argue that you'd want to only do the foundational PR and stop, but doing the whole stack of PRs gives the reviewers more information about where you're going, and allows work to continue asynchronously.
Can't you run your CI locally? I know it's not feasible for some codebase, but at least the linting, formatting, unit tests, some integration tests should be able to be done locally.
Not every project requires this, but for those that do, it's impossible.
Also, it is much harder to enforce "everyone must run each commit through the CI equivalent properly" than it is when it's on your forge.
Why can't you? That's what VMs are for. And even then, most cross-platform codebases have an abstraction layer that rarely changes. So even testing on one platform can raise your confidence very high.
> Also, it is much harder to enforce "everyone must run each commit through the CI equivalent properly"
Again why? I wouldn't care about the dev's local branch. But what is send to the main repo can be easily scripted to run the CI on every commit. You just send the result back with each commit that fails. They can replicate the same workflow on their local workspace as a pre-push process.
2. It also can't merge subsets of commits from a single PR. E.g. if you have two commits, A and B, where B depends on A... sure you can make a PR containing A and B, but if A gets approved and B doesn't, then you can't merge A.
3. The thing you want to do with a set of commits and reviewing each commit IS stacked PRs.
This is nothing to do with AI.
Whimsy is fine but that change made me super suspicious about what I was looking at.
Pre-approval the CLI tooling effectively enables easier automations around splitting a task into multiple atomic PRs - really great locally but then when you push they just show up as independent unlinked PRs.
Post-approval... they still show up as independent PRs. There's a small nav drop down up top listing the other PRs in the stack but that's it. Literally no meaningful UI changes.
The dropdown also allows you to perform a limited subset if the CLI functionality but this is similar to the ability to edit files in the UI - an optional extra casual use feature that won't be a part of dev workflows: the CLI (or IDE plugins I guess) would be the primary way to perform these actions.
It all left me wondering what the big deal with the preview not being a general release - it's extremely minor optional UI. The stacks cli has been general release since this was announced.
git-spice is specifically targeted to be useful for PR stacking and doesn't require you to do anything differently from normal git operations that you likely use already. It has a bunch of really nice flows and doesn't try to step outside the bounds of what is needed to easily stack PRs