auto-merge-pr-to-dev.yaml

name: Publish PRs in the Dev branch for preview
on:
  pull_request:
    types: [opened, labeled, synchronize, reopened]

jobs:
  merge-dev:
    if: contains(github.event.pull_request.labels.*.name, 'DEV')
    runs-on: ubuntu-latest
    steps:
      - name: Git Checkout
        uses: actions/checkout@v2
        with:
          token: ${{ secrets.DEV_DEPLOY_TOKEN }}
      - name: Merge Script
        run: |
          git --version
          git config user.name "GitHub Actions Bot"
          git config user.email "<>"
          git status
          git fetch origin dev
          git checkout dev
          git pull          
          git merge origin/${{ github.head_ref }} --no-edit -m "Merge PR ${{ github.ref_name }} to the dev branch for preview"
          git push

Custom PAT token is required if this change needs to trigger the action to actually deploy the dev branch. Otherwise, line token: ${{ secrets.DEV_DEPLOY_TOKEN }} can be omitted.