back-merge-pr.yml

name: Back-merge main to development

on:
  push:
    branches:
      - main
  workflow_dispatch:

permissions:
  contents: read
  pull-requests: write

jobs:
  open-back-merge-pr:
    runs-on: ubuntu-latest
    steps:
      - name: Checkout
        uses: actions/checkout@v4
        with:
          fetch-depth: 0

      - name: Open back-merge PR if needed
        env:
          GH_TOKEN: ${{ github.token }}
        run: |
          set -euo pipefail
          BASE_BRANCH="development"
          SOURCE_BRANCH="main"

          git fetch origin "$BASE_BRANCH" "$SOURCE_BRANCH"

          SOURCE_SHA=$(git rev-parse "origin/$SOURCE_BRANCH")
          BASE_SHA=$(git rev-parse "origin/$BASE_BRANCH")

          if [ "$SOURCE_SHA" = "$BASE_SHA" ]; then
            echo "$SOURCE_BRANCH and $BASE_BRANCH are at the same commit; nothing to back-merge."
            exit 0
          fi

          EXISTING=$(gh pr list --repo "${{ github.repository }}" \
            --base "$BASE_BRANCH" \
            --head "$SOURCE_BRANCH" \
            --state open \
            --json number \
            --jq 'length')

          if [ "$EXISTING" -gt 0 ]; then
            echo "An open PR from $SOURCE_BRANCH to $BASE_BRANCH already exists; skipping."
            exit 0
          fi

          gh pr create --repo "${{ github.repository }}" \
            --base "$BASE_BRANCH" \
            --head "$SOURCE_BRANCH" \
            --title "chore: back-merge main into development" \
            --body "Automated back-merge after changes landed on \`main\`. Review and merge to keep \`development\` in sync."

          echo "Created back-merge PR $SOURCE_BRANCH -> $BASE_BRANCH."