binder_badge.yml

name: Binder Badge
on: 
  pull_request_target:
    types: [opened, reopened]

jobs:
  binder:
    runs-on: ubuntu-latest
    steps:
    - name: comment on PR with Binder link
      uses: actions/github-script@v1
      with:
        github-token: ${{secrets.GITHUB_TOKEN}}
        script: |
          var PR_HEAD_USERREPO = process.env.PR_HEAD_USERREPO;
          var PR_HEAD_REF = process.env.PR_HEAD_REF;
          github.issues.createComment({
            issue_number: context.issue.number,
            owner: context.repo.owner,
            repo: context.repo.repo,
            body: `[![Binder](https://mybinder.org/badge_logo.svg)](https://mybinder.org/v2/gh/${PR_HEAD_USERREPO}/${PR_HEAD_REF}) :point_left: Launch a binder notebook on branch _${PR_HEAD_REF}_`
          })
      env:
        PR_HEAD_REF: ${{ github.event.pull_request.head.ref }}
        PR_HEAD_USERREPO: ${{ github.event.pull_request.head.repo.full_name }}