Any way to checkout PR from `issue_comment` event?

The example in the docs here assumes a pull request event, but it does not work when operating on Pull Request comments, since those come through the issue_comment event.

I’ve spent several hours on this now and I don’t see any way to checkout the branch associated with the issue_event.

Complications:

• The event is the comment and it links to an issue, which only indirectly seems to have data on the pull request url.
• Checking out the associate sha doesn’t give push ability, since the branch name itself is not discoverable (at least not as well as I can tell).
• Since issue_comment events have to be triggered by the workflow file on the default branch, it seems that is always the branch name provided. I haven’t yet found any way to get the actual PR branch, although it seems this should be a straightforward and frequent use case for operating on PR comments.

[Simran-B]

As the required information isn’t present in the event payload, you could use the GitHub API to fetch it. The github-script action allows you to write actions in your workflow file, which is pretty convenient:

name: Checkout PR on comment

on:
  issue_comment:
    # triggers on created, edited and deleted by default, you may wanna restrict it, e.g.:
    #types: [created]
jobs:
  pr-commented:
    name: PR commented
    if: github.event.issue.pull_request
    runs-on: ubuntu-latest
    steps:
      - uses: actions/github-script@v3
        id: get-pr
        with:
          script: |
            const request = {
              owner: context.repo.owner,
              repo: context.repo.repo,
              pull_number: context.issue.number
            }
            core.info(`Getting PR #${request.pull_number} from ${request.owner}/${request.repo}`)
            try {
              const result = await github.pulls.get(request)
              return result.data
            } catch (err) {
              core.setFailed(`Request failed with error ${err}`)
            }
      - uses: actions/checkout@v2
        with:
          repository: ${{ fromJSON(steps.get-pr.outputs.result).head.repo.full_name }}
          ref: ${{ fromJSON(steps.get-pr.outputs.result).head.sha }} # or .head.ref for branch name

[mareksuscak]

The only solution I found was to first use the checkout event and then separately use hub CLI, which is apparently installed by default and which can run hub pr checkout ${pr_num} in order to checkout whatever branch is associated with the PR (after parsing the PR num from the URL). Is there a better way?

@aaronsteers do you even need to parse it? I though the following should do:

hub pr checkout ${{ github.event.issue.number }}

This has worked for us!

deploy:
  runs-on: ubuntu-latest
  steps:
    # Checkout source code
    - name: Checkout
      uses: actions/checkout@v2
    - name: Checkout Pull Request
      run: hub pr checkout ${{ github.event.issue.number }}
      env:
        GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}