promote-main-to-stable.yml

# Promote Main to Stable Workflow
#
# Creates a promotional PR to sync the stable branch with main.
# Runs automatically every Sunday night (midnight UTC) and can be triggered manually.
#
# This workflow:
#   1. Checks if stable is behind main
#   2. Creates a PR from main -> stable if there are new changes
#   3. Reuses an existing open PR if one already exists

name: Promote Main to Stable

on:
  schedule:
    - cron: '0 0 * * 0'  # Every Sunday at midnight UTC
  workflow_dispatch:

permissions:
  contents: read
  pull-requests: write

env:
  GH_USER_NAME: github-actions[bot]
  GH_USER_EMAIL: github-actions[bot]@users.noreply.github.com

jobs:
  promote:
    name: Create Promotion PR
    runs-on: ubuntu-latest

    steps:
      - name: Checkout repository
        uses: actions/checkout@v6
        with:
          fetch-depth: 0
          token: ${{ secrets.GITHUB_TOKEN }}

      - name: Configure Git
        run: |
          git config user.name "${{ env.GH_USER_NAME }}"
          git config user.email "${{ env.GH_USER_EMAIL }}"

      - name: Promote main to stable
        env:
          GH_TOKEN: ${{ secrets.GITHUB_TOKEN }}
        run: |
          git fetch origin main stable

          DIFF_COUNT=$(git rev-list --count origin/stable..origin/main)
          if [ "$DIFF_COUNT" -eq 0 ]; then
            echo "stable is already up to date with main. Nothing to promote."
            echo "## Promote Main to Stable" >> "$GITHUB_STEP_SUMMARY"
            echo "stable is already up to date with main. No PR needed." >> "$GITHUB_STEP_SUMMARY"
            exit 0
          fi

          echo "Found $DIFF_COUNT commit(s) to promote from main to stable."

          COMMIT_LOG=$(git log --oneline origin/stable..origin/main --no-merges | head -30)
          BODY="Automated promotion of **${DIFF_COUNT} commit(s)** from \`main\` to \`stable\`."
          BODY="${BODY}"$'\n\n'"\`\`\`"$'\n'"${COMMIT_LOG}"$'\n'"\`\`\`"

          EXISTING_PR=$(gh pr list --base stable --head main --state open --json number --jq '.[0].number // empty')

          if [ -n "$EXISTING_PR" ]; then
            if ! echo "$BODY" | gh pr edit "$EXISTING_PR" --body-file -; then
              echo "::error::Failed to update existing promotion PR #${EXISTING_PR}"
              exit 1
            fi
            echo "Updated existing promotion PR #${EXISTING_PR}"
          else
            if ! echo "$BODY" | gh pr create --base stable --head main \
              --title "chore: promote main to stable" \
              --body-file -; then
              echo "::error::Failed to create promotion PR"
              exit 1
            fi
            echo "Created new promotion PR"
          fi