squash-pr.yml

# .github/workflows/squash-pr.yml

name: Squash Commits

on:
  pull_request:
    types:
      - labeled

permissions:
  # Permissions are still useful for the initial checkout and reading PR data
  contents: read
  pull-requests: read

jobs:
  squash:
    if: github.event.label.name == 'squash-and-merge'
    runs-on: ubuntu-latest

    steps:
      # Step 1: Checkout using the PAT to have write access later
      - name: Checkout PR Branch
        uses: actions/checkout@v4
        with:
          # Use the PAT so we can push back to the repo
          token: ${{ secrets.ACTIONS_PAT }}
          ref: ${{ github.event.pull_request.head.ref }}
          fetch-depth: 0

      # Step 2: Configure git with the user associated with the PAT
      # This makes the commit appear from a user, not a bot
      - name: Configure Git User
        run: |
          # Use a real user's info (or a dedicated bot user)
          # to ensure other actions are triggered.
          git config user.name "Your Name or Bot Name"
          git config user.email "your-email@example.com"

      # Step 3: Squash commits and create a detailed commit message
      - name: Squash Commits and Generate Message
        run: |
          set -e # Exit on error
          BASE_BRANCH=${{ github.event.pull_request.base.ref }}
          MERGE_BASE=$(git merge-base origin/$BASE_BRANCH HEAD)
          
          echo "Found merge base: $MERGE_BASE"

          # --- GENERATE COMMIT MESSAGE ---
          # 1. Get the subject from the very first commit
          COMMIT_SUBJECT=$(git log --reverse --format=%s $MERGE_BASE..HEAD | head -n 1)
          
          # 2. Get a formatted list of all commit messages for the body
          COMMIT_BODY=$(git log --format="* %s (%h)" $MERGE_BASE..HEAD)

          # --- GENERATE CO-AUTHOR TRAILERS ---
          # 3. Get the name and email of the user running the commit
          COMMITTER_INFO="$(git config user.name) <$(git config user.email)>"

          # 4. Get a unique, sorted list of all other authors
          # The "|| true" prevents the script from failing if grep finds no other authors
          CO_AUTHORS=$(git log --format="%an <%ae>" $MERGE_BASE..HEAD | sort -u | grep -vF "$COMMITTER_INFO" || true)

          # 5. Build the "Co-authored-by:" trailers
          TRAILERS=""
          if [ -n "$CO_AUTHORS" ]; then
            while IFS= read -r AUTHOR; do
              TRAILERS="${TRAILERS}Co-authored-by: ${AUTHOR}\n"
            done <<< "$CO_AUTHORS"
          fi

          # --- PERFORM THE SQUASH AND COMMIT ---
          echo "New commit subject: $COMMIT_SUBJECT"
          
          # Add a check to prevent empty commits
          if [ -z "$COMMIT_SUBJECT" ]; then
            echo "Could not determine a commit subject. Aborting."
            exit 1
          fi
          
          git reset --soft $MERGE_BASE
          
          # Create the new commit with the subject, body, AND co-author trailers
          # The -m flags are concatenated to form the final message.
          git commit -m "$COMMIT_SUBJECT" -m "$COMMIT_BODY" -m "$TRAILERS"


      # Step 4: Force-push the squashed commit
      - name: Force-Push to PR Branch
        run: |
          BRANCH_NAME=${{ github.event.pull_request.head.ref }}
          git push --force origin HEAD:$BRANCH_NAME