Automatically sync branches via Github Action

sync_branches.yaml

name: Sync branches master -> release -> develop

on:
  push:
    branches:
      - release
      - master

jobs:
  sync-release:
    name: Sync branches after a PR was merged
    runs-on: ubuntu-latest
    steps:
      - name: checkout
        uses: actions/checkout@v3

      - name: decide target branch
        id: set-target-branch
        run: |
          if [[ ${{ github.ref_name }} == 'master' ]]; then
            echo "::set-output name=target-branch::release"
          else
            echo "::set-output name=target-branch::develop"
          fi

      - name: merge branch to target
        uses: mtanzi/action-automerge@v1
        with:
          github_token: ${{ secrets.REPO_PAT }}
          source: ${{ github.ref_name }}
          target: ${{ steps.set-target-branch.outputs.target-branch }}