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cheap-merge-queue

A ~30-line GitHub Action that mimics GitHub's Enterprise-only merge queue on Teams/Free plans.

What it does

On every push to main, walks all open PRs targeting main that have auto-merge enabled and calls the REST "Update branch" endpoint on each. PRs without auto-merge are left alone (they're still being iterated on). PRs with conflicts are skipped (logged, not failed).

Using auto-merge as the signal is the point: the author has explicitly said "this is ready — land it when the gates open." Everything else is in-progress and shouldn't be churned.

Combined with the branch protection rule "Require branches to be up to date before merging", this is effectively a serial merge queue: no PR can land against a stale main.

Usage (copy/paste approach)

  1. Copy .github/workflows/auto-update-prs.yml into your repo.
  2. Enable branch protection on main:
    • Require status checks to pass
    • Require branches to be up to date before merging ← this is the one
  3. Done.

Why not use GitHub's built-in merge queue?

It's Enterprise-only. This file is free.

Limitations vs. a real merge queue

  • No batching (can't test A+B+C together to land them faster).
  • Tiny race window: if A merges and B's merge button is clicked within ~seconds before the workflow fires, B could land stale — but the "up to date" branch protection rule rejects that.
  • Uses the default GITHUB_TOKEN, so pushes from this workflow don't trigger other workflows (GitHub's loop-prevention). If you need downstream CI to re-run on the updated branch, swap in a PAT or GitHub App token.