Automerge pre-commit.ci autoupdate PRs

[kluge7]

Context

We’re currently using pre-commit for local and CI linting/formatting hooks.
Updates to these hooks are handled automatically through pre-commit.ci, configured with:

ci:
  autoupdate_schedule: quarterly

This means that every few months, pre-commit.ci will open an automated pull request (e.g. “[pre-commit.ci] pre-commit autoupdate”) with updated hook versions.

Motivation

These auto-update PRs require a manual approval and merge each time — even though:

• They are generated by a trusted bot (pre-commit-ci[bot])
• All CI and formatting checks must already pass before merge
  This adds unnecessary overhead for a purely maintenance task.

Proposed Solution

Enable automatic merging of pre-commit.ci’s autoupdate PRs once all required checks have passed.

We’ve investigated this and found that:

• Pre-commit.ci does not provide a built-in auto-merge option (confirmed in issue #48)
• GitHub’s built-in auto-merge feature is limited, as it cannot be restricted to specific actors such as bots (https://docs.github.com/en/pull-requests/collaborating-with-pull-requests/incorporating-changes-from-a-pull-request/automatically-merging-a-pull-request)
• We can use Mergify to handle automatic merging.
  • It has already been installed as a GitHub App and connected to the vortex-ci repository.

Tasks

• Research whether auto-merging pre-commit.ci autoupdate PRs is possible using Mergify.
• Set up a test repository to experiment with a .mergify.yml configuration (this should be done a personal repo and you must install Mergify as a GitHub App)
• Verify that auto-merge triggers only for PRs created by pre-commit-ci[bot].
• Ensure all required CI checks pass before any auto-merge is performed (add an example GitHub actions workflow to test on)
• Document the setup steps and results (e.g., limitations, required permissions, etc.).
• If successful, propose integrating the solution into the vortex-ci repository and other repositories that use pre-commit autoupdate

References:

• pre-commit.ci documentation — Continuous integration service for pre-commit hooks
• pre-commit documentation — General usage, configuration, and hook management
• Mergify documentation — YAML-based automation and merge queue configuration
• Mergify App on GitHub Marketplace — Installation and permissions
• pre-commit-ci/issues#48 — Discussion confirming that auto-merge is not built into pre-commit.ci

Contacts

@kluge7
@Andeshog