name: Format

on:
  push:
    branches:
      - main
  # PRs get the same gate -- without this the checks only ran after merge.
  pull_request:

jobs:
  clang-format:
    runs-on: ubuntu-latest

    steps:
      - name: Check out repository
        uses: actions/checkout@v7

      - name: Install clang-format
        # Pinned to 18 so CI matches the version contributors run locally;
        # clang-format output differs between major versions.
        run: |
          sudo apt-get update
          sudo apt-get install -y clang-format-18

      - name: Check formatting
        # Fails the job (and blocks the PR) the moment any file differs from
        # the Linux kernel .clang-format style. Run `make format` to fix.
        run: make check