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A Better Model for Stacked (GitHub) Pull Requests

https://timothya.com/blog/git-stack/ has interactive examples

Basic idea

The only real solution to this problem (that I know of, anyway) is the notion of stacked PRs. Here's the basic idea:

  • Create a pull request from a feature branch (say feature-1) to master
  • Create a second pull request from another feature branch (say feature-2) to feature-1
  • Repeat until you have a stack of pull requests
  • When it's time to merge, start from the topmost PR (the one that's furthest from master) and merge/rebase every PR in until you merge the entire stack in to master

Benefits

After having used the stacked PR workflow for a while, the benefits are readily apparent:

  1. Dependencies: Changes that your feature depends on (but are otherwise unrelated) can go in a separate PR.
  2. Reviewers: Every PR in the stack can potentially be assigned to a different set of reviewers, which can be helpful in a few different contexts - ramping, areas of expertise, or workload.
  3. Incremental approval: Large, thorny changes can be approved in pieces.

Tradeoffs

The stacked PR workflow in general can be very useful, but it isn't a silver bullet. There are concerns & tradeoffs to consider:

  1. You can't create a stack of pull requests if you're on a fork.
  2. Force-pushes are pretty much a requirement, so this doesn't work well for collaborative feature branches.
  3. There's more initial overhead for the author; it's a lot easier (at first, anyway) to stick the entire change in the single PR.

Conclusion

Ultimately, stacking PRs is just another tool to help manage GitHub-based code review. I've found that it works well for large changes (4+ PRs), but small-to-medium changes are generally better off as commits on a single PR. There's undoubtedly some discretion that needs to be applied here, but don't be afraid to use a stack of PRs if the situation calls for it!

The tooling situation is not great, admittedly. I haven't found another tool that does what gh-stack does, and there's a lot of room for improvement there. I'm also hoping for something GitHub-native in the near future. 🤞

As for immediate next steps, I want to add functionality to gh-stack so it creates the initial set of PRs on Github for you. Right now you have to create them manually and make sure each PR has the right merges into value set, which can be somewhat error prone.