upstream-sync.yml

name: Sync Release with Upstream

on:
  schedule:
    # Runs every 5 minutes
    - cron: '*/5 * * * *'

  # Allows you to manually trigger the workflow from the Actions tab
  workflow_dispatch:

jobs:
  sync:
    runs-on: ubuntu-latest

    steps:
      - name: Checkout the forked repository
        uses: actions/checkout@v3
        with:
          token: ${{ secrets.GITHUB_TOKEN }}
          persist-credentials: false # We disable this because we will be using a different token

      - name: Check for UPSTREAM_URL and UPSTREAM_SYNC_BRANCH_NAME in environment
        id: check_variables
        run: |
          if [ -z "${{ vars.UPSTREAM_URL }}" ]; then
            echo "UPSTREAM_URL environment variable does not exist."
            echo "HAS_UPSTREAM=false" >> $GITHUB_ENV
          else
            echo "UPSTREAM_URL environment variable found."
            echo "HAS_UPSTREAM=true" >> $GITHUB_ENV
            echo "UPSTREAM_URL=${{ vars.UPSTREAM_URL }}" >> $GITHUB_ENV
          fi

          if [ -z "${{ vars.UPSTREAM_SYNC_BRANCH_NAME }}" ]; then
            echo "UPSTREAM_SYNC_BRANCH_NAME environment variable does not exist."
            echo "HAS_SYNC_BRANCH=false" >> $GITHUB_ENV
          else
            echo "UPSTREAM_SYNC_BRANCH_NAME environment variable found."
            echo "HAS_SYNC_BRANCH=true" >> $GITHUB_ENV
            echo "UPSTREAM_SYNC_BRANCH_NAME=${{ vars.UPSTREAM_SYNC_BRANCH_NAME }}" >> $GITHUB_ENV
          fi

      - name: Configure git for GitHub Actions
        if: env.HAS_UPSTREAM == 'true' && env.HAS_SYNC_BRANCH == 'true'
        run: |
          git config user.name "github-actions[bot]"
          git config user.email "github-actions[bot]@users.noreply.github.com"

      - name: Add the upstream repository
        if: env.HAS_UPSTREAM == 'true' && env.HAS_SYNC_BRANCH == 'true'
        run: git remote add upstream ${{ env.UPSTREAM_URL }}

      - name: Check for differences between local and upstream branch, excluding .github/workflows
        if: env.HAS_UPSTREAM == 'true' && env.HAS_SYNC_BRANCH == 'true'
        run: |
          git fetch upstream
          git fetch origin

          # Check if the branch exists on the remote
          if git show-ref --verify --quiet refs/remotes/origin/${{ env.UPSTREAM_SYNC_BRANCH_NAME }}; then
            echo "Branch ${{ env.UPSTREAM_SYNC_BRANCH_NAME }} exists on remote."
            # Compare origin branch with upstream, excluding .github/workflows
            git diff --quiet origin/${{ env.UPSTREAM_SYNC_BRANCH_NAME }} upstream/main -- . ':(exclude).github/workflows' || echo "CHANGES_DETECTED=true" >> $GITHUB_ENV
          else
            echo "Branch ${{ env.UPSTREAM_SYNC_BRANCH_NAME }} does not exist on remote."
            # Compare upstream/main with itself to force no changes
            git diff --quiet upstream/main upstream/main -- . ':(exclude).github/workflows' || echo "CHANGES_DETECTED=false" >> $GITHUB_ENV
          fi

      - name: Fetch all branches from the upstream repository
        if: env.HAS_UPSTREAM == 'true' && env.HAS_SYNC_BRANCH == 'true' && env.CHANGES_DETECTED == 'true'
        run: git fetch upstream

      - name: Set up authentication
        if: env.HAS_UPSTREAM == 'true' && env.HAS_SYNC_BRANCH == 'true' && env.CHANGES_DETECTED == 'true'
        run: |
          git remote set-url origin https://${{ github.actor }}:${{ secrets.GITHUB_TOKEN }}@github.com/${{ github.repository }}
        env:
          GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
          GITHUB_ACTOR: ${{ github.actor }}

      - name: Merge upstream/main into forked repo branch
        if: env.HAS_UPSTREAM == 'true' && env.HAS_SYNC_BRANCH == 'true' && env.CHANGES_DETECTED == 'true'
        run: |
          git checkout -B ${{ env.UPSTREAM_SYNC_BRANCH_NAME }} upstream/main

          # GitHub Actions worker doesn't have the correct permissions to checked in
          # modified workflow files. To workaround this, we'll remove all files in 
          # .github/workflows that doesn't exist on the remote

          # Remove files not on the remote
          rm -rf .github/workflows

          # Check if the deploy branch exists on the remote
          if git ls-remote --exit-code --heads origin ${{ env.UPSTREAM_SYNC_BRANCH_NAME }}; then
            # Mirror remote workflows if they exist
            if git ls-tree --name-only -r origin/${{ env.UPSTREAM_SYNC_BRANCH_NAME }}:.github/workflows &> /dev/null; then
              git checkout origin/${{ env.UPSTREAM_SYNC_BRANCH_NAME }} .github/workflows
            fi
          fi

          git commit -am "Prepare branch for deploy"
          git push -f origin ${{ env.UPSTREAM_SYNC_BRANCH_NAME }}
        env:
          GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
          GITHUB_ACTOR: ${{ github.actor }}