.github/workflows/reusable_sync_to_main.yml

name: Reusable Sync To Main
on:
  workflow_call:
    inputs:
      branch-name:
        description: 'The release branch to sync back to main.'
        required: true
        type: string
      comment-if-exists:
        description: >-
          If non-empty, this is posted as a comment when the sync PR already
          exists. The comment is only posted once per PR.
        required: false
        default: ''
        type: string
    secrets:
      BOT_TOKEN:
        required: true
jobs:
  sync_to_main:
    if: github.repository_owner == 'flutter'
    runs-on: ubuntu-latest
    permissions:
      # Need write permission to create PR.
      contents: write
      pull-requests: write
    steps:
      - name: Checkout repository
        uses: actions/checkout@9c091bb21b7c1c1d1991bb908d89e4e9dddfe3e0
        with:
          ref: ${{ inputs.branch-name }}
          fetch-depth: 0 # Fetch history to allow branch comparison
          persist-credentials: false

      - name: Create Pull Request
        env:
          GH_TOKEN: ${{ secrets.BOT_TOKEN }}
          BRANCH_NAME: ${{ inputs.branch-name }}
          COMMENT: ${{ inputs.comment-if-exists }}
          # Used to avoid posting the same comment on every scheduled run.
          COMMENT_MARKER: '<!-- batch-release-sync-nudge -->'
        run: |
          gh auth setup-git
          # 1. Fetch main so the runner can see the difference
          git fetch origin main

          # 2. Check if PR already exists before creating
          EXISTING_PR=$(gh pr list --head "${BRANCH_NAME}" --base "main" --json number --jq '.[0].number')
          if [ -n "$EXISTING_PR" ]; then
            echo "A pull request for ${BRANCH_NAME} already exists (#${EXISTING_PR})."
            if [ -n "$COMMENT" ]; then
              if gh pr view "$EXISTING_PR" --json comments --jq '.comments[].body' | grep -qF "$COMMENT_MARKER"; then
                echo "Already commented on #${EXISTING_PR}."
              else
                gh pr comment "$EXISTING_PR" --body "${COMMENT} ${COMMENT_MARKER}"
              fi
            fi
            exit 0
          fi

          # 3. Verify there are actually new commits to sync.
          # This prevents the "GraphQL: No commits between main..." error, and is
          # the expected state when the release PR itself has not landed yet.
          COMMITS_COUNT=$(git rev-list --count origin/main..HEAD)

          if [ "$COMMITS_COUNT" -eq "0" ]; then
            echo "No new commits found on ${BRANCH_NAME} compared to main. Nothing to sync."
            exit 0
          fi

          # 4. Extract package name for label. Package names can't contain a
          # hyphen, so everything from the first one on is the version.
          TEMP="${BRANCH_NAME#release-}"
          PACKAGE_NAME="${TEMP%%-*}"

          # 5. Create the PR directly
          gh pr create \
            --base "main" \
            --head "${BRANCH_NAME}" \
            --title "Sync ${BRANCH_NAME} to main" \
            --body "This automated PR syncs the changes from the release branch ${BRANCH_NAME} back to the main branch." \
            --label "override: batch-${PACKAGE_NAME}"