check_fork_status.yaml

name: Check Fork Status and Notify

on:
  pull_request:
    types: [opened, synchronize]  # Trigger when a PR is opened or updated

permissions:
  pull-requests: write  # Allow posting comments on PRs

jobs:
  check_fork:
    runs-on: ubuntu-latest

    steps:
      - name: Checkout the repository
        uses: actions/checkout@v3
        with:
          fetch-depth: 2  # Fetch enough history to compare branches

      - name: Fetch the latest base branch
        run: |
          git fetch origin main  # Replace 'main' with your base branch if different

      - name: Check if the branch is up to date
        id: check_fork
        run: |
          # Compare the contributor's branch with the base branch (main)
          behind_count=$(git rev-list --right-only --count HEAD...origin/main)
          echo "::set-output name=behind::$behind_count"

      - name: Comment on the PR if fork is outdated
        if: steps.check_fork.outputs.behind != '0'  # If the fork is behind
        uses: actions/github-script@v7
        with:
          script: |
            const prNumber = context.payload.pull_request.number;
            const owner = context.repo.owner;
            const repo = context.repo.repo;

            await github.rest.issues.createComment({
              owner: owner,
              repo: repo,
              issue_number: prNumber,
              body: '⚠️ It looks like your branch is out of date with the base branch. Please sync your fork and update the PR.'
            });