check-stage0.yml

name: Check for stage0 changes

on:
  merge_group:
  pull_request:

jobs:
  check-stage0-on-queue:
    runs-on: ubuntu-latest
    steps:
    - uses: actions/checkout@v6
      with:
        ref: ${{ github.event.pull_request.head.sha }}
        fetch-depth: 0
        filter: tree:0

    - name: Find base commit
      if: github.event_name == 'pull_request'
      run: echo "BASE=$(git merge-base origin/${{ github.base_ref }} HEAD)" >> "$GITHUB_ENV"

    - name: Identify stage0 changes
      run: |
        git diff "${BASE:-HEAD^}..HEAD" --name-only -- stage0/stdlib > "$RUNNER_TEMP/stage0" || true
        if test -s "$RUNNER_TEMP/stage0"
        then
          echo "CHANGES=yes" >> "$GITHUB_ENV"
        else
          echo "CHANGES=no" >> "$GITHUB_ENV"
        fi
      shell: bash

    - if: github.event_name == 'pull_request'
      name: Set label
      uses: actions/github-script@v8
      with:
        script: |
          const { owner, repo, number: issue_number  } = context.issue;
          if (process.env.CHANGES == 'yes') {
            await github.rest.issues.addLabels({ owner, repo, issue_number, labels: ['changes-stage0'] }).catch(() => {});
          } else {
            await github.rest.issues.removeLabel({ owner, repo, issue_number, name: 'changes-stage0' }).catch(() => {});
          }

    - if: env.CHANGES == 'yes'
      name: Report changes
      run: |
        echo "Found changes to stage0/, please do not merge using the merge queue." | tee "$GITHUB_STEP_SUMMARY"
        # shellcheck disable=SC2129
        echo '```'                  >> "$GITHUB_STEP_SUMMARY"
        cat  "$RUNNER_TEMP/stage0"  >> "$GITHUB_STEP_SUMMARY"
        echo '```'                  >> "$GITHUB_STEP_SUMMARY"

    - if: github.event_name == 'merge_group' && env.CHANGES == 'yes'
      name: Fail when on the merge queue
      run: exit 1