back-merge-pr.yml

name: Back-merge master to development

on:
  push:
    branches:
      - master
  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="master"

          git fetch origin "$BASE_BRANCH" "$SOURCE_BRANCH"

          if ! git show-ref --verify --quiet "refs/remotes/origin/$BASE_BRANCH"; then
            echo "Base branch '$BASE_BRANCH' does not exist on origin; skipping."
            exit 0
          fi

          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 $SOURCE_BRANCH into $BASE_BRANCH"             --body "Automated back-merge after changes landed on \\`$SOURCE_BRANCH\\`. Review and merge to keep \\`$BASE_BRANCH\\` in sync."

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