github-actions-fetching-upstream.yml

name: Fetch Upstream

on: pull_request

jobs:
  fetch-upstream:
    runs-on: ubuntu-latest
    steps:
    - uses: actions/checkout@master
    - name: fetch and push
      env:
        GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
        UPSTREAM: https://github.com/babel/babel
      run: |       
        git config --global user.name "github-actions"
        git config --global user.email "github-actions@users.noreply.github.com"
        
        # inspired by https://dev.to/ranewallin/how-to-keep-your-forked-repository-current-38mn
        
        # If you haven't already added an upstream source, set your upstream
        # to the fork's original source
        git remote add upstream "${UPSTREAM}"
        
        # Remote with access for pushing
        git remote add fork "https://x-access-token:${GITHUB_TOKEN}@github.com/${GITHUB_REPOSITORY}.git"
        
        # Verify upstream is correct, you should see the URL for the upstream fetch and push 
        git remote -v
        
        # Get all recent branches and commits from the upstream
        git fetch upstream
        
        # Merge the branches and commits from the upstream
        git merge upstream/master
                
        # helpful for debugging
        git show-ref
        
        # Set upstream branch and push to the forked remote repo
        git checkout -b upstream
        git push -u fork upstream