fast-forward.yml

# Github UI does not support merges that preserve the commit revision of the PR
# branch (fast forward merging).
#
# See also this issue: https://github.com/community/community/discussions/4618
#
# Since we store benchmark results from PRs with the revision information from
# the PR branch, ideally we'd like to preserve the results that we stored for a
# given revision while developing on the feature branch and still be able to
# lookup results on a commit id once it lands in main. If the commit IDs change
# that makes it harder.
#
# Hence this script allows to do a fast-forward merge by commenting
# /fast-forward on the PR. With /fast-forward the commit IDs are preserved
# between the feature branch and the main branch.
name: Fast-forward

on:
  issue_comment:
    types: [created, edited]

jobs:
  fast_forward:
    name: Fast-forward
    runs-on: [self-hosted, Linux, skylake-2x]
    if: |
      github.event.issue.pull_request &&
      contains(github.event.comment.body, '/fast-forward')

    steps:

      - name: Fetch repository
        uses: actions/checkout@v3
        with:
          fetch-depth: 0

      - name: Checkout pull request
        run: hub pr checkout ${{ github.event.issue.number }}
        env:
          GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}

      - name: Fast-forward & push
        run: |
          export PR_COMMIT=$(git rev-parse HEAD)
          git checkout main
          git merge --ff-only "$PR_COMMIT"
          git push origin main