finalize-release.yml

name: Finalize Release

on:
  pull_request:
    types: [closed]
    branches: [main]

jobs:
  finalize-release:
    name: Tag, Release, and Back-merge
    if: github.event.pull_request.merged == true && startsWith(github.event.pull_request.head.ref, 'release/')
    runs-on: ubuntu-latest
    permissions:
      contents: write
      pull-requests: write
    steps:
      - name: Checkout release merge commit
        uses: actions/checkout@v5
        with:
          ref: ${{ github.event.pull_request.merge_commit_sha }}
          fetch-depth: 0
          token: ${{ secrets.RELEASE_PAT }}

      - name: Configure Git
        run: |
          git config user.name "github-actions[bot]"
          git config user.email "github-actions[bot]@users.noreply.github.com"

      - name: Extract release info from branch name
        id: release
        env:
          RELEASE_BRANCH: ${{ github.event.pull_request.head.ref }}
        shell: bash
        run: |
          BRANCH="$RELEASE_BRANCH"
          TAG="${BRANCH#release/}"
          SEMVER="${TAG#v}"

          if echo "$SEMVER" | grep -q '-'; then
            PRERELEASE="true"
          else
            PRERELEASE="false"
          fi

          echo "tag=${TAG}" >> "$GITHUB_OUTPUT"
          echo "semver=${SEMVER}" >> "$GITHUB_OUTPUT"
          echo "prerelease=${PRERELEASE}" >> "$GITHUB_OUTPUT"

      - name: Check if tag already exists
        shell: bash
        run: |
          if git rev-parse "${{ steps.release.outputs.tag }}" >/dev/null 2>&1; then
            echo "::error::Tag ${{ steps.release.outputs.tag }} already exists."
            exit 1
          fi

      - name: Create annotated tag
        shell: bash
        run: |
          TAG="${{ steps.release.outputs.tag }}"
          git tag -a "$TAG" -m "Release $TAG"
          git push origin "$TAG"

      - name: Create GitHub Release
        env:
          GH_TOKEN: ${{ secrets.RELEASE_PAT }}
          TAG: ${{ steps.release.outputs.tag }}
          PRERELEASE: ${{ steps.release.outputs.prerelease }}
        shell: bash
        run: |
          PRERELEASE_FLAG=""
          if [ "$PRERELEASE" = "true" ]; then
            PRERELEASE_FLAG="--prerelease"
          fi

          gh release create "$TAG" \
            --title "$TAG" \
            --generate-notes \
            $PRERELEASE_FLAG

      - name: Delete release branch
        env:
          RELEASE_BRANCH: ${{ github.event.pull_request.head.ref }}
        shell: bash
        run: |
          BRANCH="$RELEASE_BRANCH"
          git push origin --delete "$BRANCH" || true

      - name: Create back-merge PR
        env:
          GH_TOKEN: ${{ secrets.RELEASE_PAT }}
          TAG: ${{ steps.release.outputs.tag }}
        shell: bash
        run: |
          BACKMERGE_BRANCH="backmerge/${TAG}"

          git checkout -b "$BACKMERGE_BRANCH" "${{ github.event.pull_request.merge_commit_sha }}"
          git push origin "$BACKMERGE_BRANCH"

          gh pr create \
            --base develop \
            --head "$BACKMERGE_BRANCH" \
            --title "Back-merge ${TAG} from main into develop" \
            --body "Automatic back-merge after release ${TAG}. Merge this to keep \`develop\` in sync with \`main\`."