Merge release branch to master & create tag

merge-release-branch-to-master-and-create-tag.yml

name: 'Merge `release/x.x.x` to master & create x.x.x tag'
on:
  pull_request:
    types:
      - opened
jobs:
  create-tag:
    runs-on: ubuntu-latest
    if: startsWith(github.event.pull_request.head.ref, 'release/')
    steps:
      - name: Create tag
        id: create_tag
        run: |
          tag=$(echo ${{ github.event.pull_request.head.ref }} | sed 's/release\///')
          echo ::set-output name=tag::$tag
      - uses: actions/checkout@v2
      - run: |
          git tag ${{ steps.create_tag.outputs.tag }}
          git push origin ${{ steps.create_tag.outputs.tag }}

  merge-to-master:
    runs-on: ubuntu-latest
    if: startsWith(github.event.pull_request.head.ref, 'release/')
    steps:
      - uses: mtanzi/action-automerge@v1
        with:
          github_token: ${{ github.token }}
          source: ${{ github.event.pull_request.head.ref }}
          target: 'master