A GitHub Actions workflow that automatically links stacked pull requests and prevents them from being merged out of order.

Large pull requests are hard to review. Stacking lets you break a big change into small, focused PRs where each one builds on the previous. Because each PR targets the branch of the one before it, reviewers only see the diff between two adjacent steps, not the entire change at once. This makes reviews faster, more thorough, and easier to reason about.

The trade-off is bookkeeping. With a stack of PRs, you need to merge them in order (top of the stack first, working your way down), and it's easy to lose track of which PR depends on which. Someone might merge a PR before its dependencies are ready, or not realize that a PR is part of a stack at all.

ReviewBot handles that bookkeeping for you. It links the PRs together, reminds you of the merge order, and converts the root PR to a draft until all children above it are merged. You start by reviewing the root PR (which is now a draft) to get the big picture, but you don't merge it yet. Then you go to the first child PR, review it, and merge it. GitHub automatically updates the next child's base branch, so its diff stays clean and only shows its own changes. You continue working through the stack this way until all children are merged and the root PR is ready to go.

When a pull request is opened or reopened, ReviewBot checks whether the PR's base branch has its own open pull request. If it does, the workflow:

• Comments on both the new PR and the base PR with links to each other.
• If the base PR targets the default branch (i.e. it's the root of the stack), converts it to a draft so it can't be merged prematurely.
• If the base PR is an intermediate PR in the stack, adds a comment reminding you to merge it first.

Copy .github/workflows/ReviewBot.yml into your repository. That's it.

The workflow uses GITHUB_TOKEN, which is provided automatically by GitHub Actions. No additional secrets or configuration needed.

Say you have three branches forming a stack:

main <- feature-auth <- feature-auth-tests <- feature-auth-docs

Each branch has a PR targeting the one before it. When you open the PR for feature-auth-tests (targeting feature-auth), ReviewBot will:

1. Comment on the feature-auth-tests PR, linking to the feature-auth PR.
2. Comment on the feature-auth PR, notifying about the new child.
3. Since feature-auth targets main (the default branch), convert it to a draft.

When you then open the PR for feature-auth-docs (targeting feature-auth-tests), ReviewBot will link them and remind you to merge feature-auth-tests first.

GitHub is building a native stacked PRs feature called gh-stack with a dedicated CLI, UI stack navigator, automatic rebasing, batch merging, and CI that evaluates against the final target branch. It is currently in private preview.

Use this bot if you want a zero-config, drop-in solution that works today on any repo. It requires no CLI tooling and no feature flags — just one workflow file.

Use gh-stack if you need local workflow tooling (gs init, gs add, gs push), automatic rebasing after partial merges, merge queue integration, or proper branch protection semantics against the final target branch. Once gh-stack is generally available, it will cover everything this bot does and more.

• The workflow only runs on opened and reopened events. If you change a PR's base branch after opening it, ReviewBot won't pick that up.
• ReviewBot adds comments but does not remove or update them. If a child PR is closed, the comments on the parent will remain.
• The draft conversion only applies to the root PR (the one targeting the default branch). Intermediate PRs in the stack are not converted to drafts.

MIT