Checkout: Any way to checkout PR from `issue_comment` event?

[aaronsteers]

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.

[aaronsteers]

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).

name: Slash Command CI

on: issue_comment

jobs:
  check_comments:
    runs-on: ubuntu-latest
    name: Check comments for /format
    steps:
      - name: Clone git repo
        uses: actions/checkout@v2
      - name: Checkout Pull Request
        env:
          GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
        run: |
          PR_URL="${{ github.event.issue.pull_request.url }}"
          PR_NUM=${PR_URL##*/}
          echo "Checking out from PR #$PR_NUM based on URL: $PR_URL"
          hub pr checkout $PR_NUM
      - name: Configure Git Agent
        run: |
          git config --global user.email "[email protected]"
          git config --global user.name "Me, Not Really (CI bot)"
      - uses: hashicorp/setup-terraform@v1
        with:
          terraform_version: 0.13.0
      - run: terraform fmt -recursive
      - run: git commit -a -m "GitOps Bot (Autoformat)"
      - run: git push

Is there a better way?

[NutanNiraula]

I faced the same problem with one more restriction that github account was not owned by us, I don't know the context that other users will face but in my case I can just send in the branch name through the comment. so, here is what I did:

Basically pull out branch name from comment where branch name is enclosed in [], i.e [branch_name] then extract out the name to pass it to the checkout action. I would love to find better way than this but for now it works ok.

steps:
    - name: Get Branch name
      id: branchName
      run: |
        echo ::set-output name=branch::$(echo $PR_COMMENT | cut -d "[" -f2 | cut -d "]" -f1)
      env:
        PR_COMMENT: ${{ github.event.comment.body }}
    - name: Checkout code
      uses: actions/checkout@v2
      with: 
        ref: ${{ steps.branchName.outputs.branch }}

[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