How to get base_ref/head_ref on event issue_comment triggered from a pull request ?

[LPauzies]

Select Topic Area

Question

Body

Hello,
I'm currently trying to trigger a workflow when a comment is written in a Pull Request. However, I'm not able to get the base_ref/head_ref to checkout on the branch I want (In my case, I need to get head_ref).

According to the documentation, we should use issue_comment, but previously it was existing a pull_request_comment that seems to be not handled anymore.

So what is the workaround to get head_ref branch when triggering a workflow from a comment done in a Pull Request ?

Here is a piece of code to demonstrate this :

name: A pipeline

on:
  issue_comment:
    types: [ created ]

jobs:
  build:
    runs-on: ubuntu-latest
    if: github.event.issue.pull_request && contains(github.event.comment.body, '/build')
    steps:
      - uses: actions/checkout@v3
        name: Checkout the given branch
        with:
          ref: ${{ github.ref }} # Should be head_ref and not "master" or default branch
          fetch-depth: 0

      - name: Dump GitHub context
        env:
          GITHUB_CONTEXT: ${{ toJson(github) }}
        run: echo "$GITHUB_CONTEXT"

[seanglynn-thrive]

@LPauzies it's possible to derive the PR number from the event metadata (github.event.issue.number) and check out the branch from that.
This solution worked for me:
actions/checkout#331 (comment)

[github-actions[bot]]

🕒 Discussion Activity Reminder 🕒

This Discussion has been labeled as dormant by an automated system for having no activity in the last 60 days. Please consider one the following actions:

1️⃣ Close as Out of Date: If the topic is no longer relevant, close the Discussion as out of date at the bottom of the page.

2️⃣ Provide More Information: Share additional details or context — or let the community know if you've found a solution on your own.

3️⃣ Mark a Reply as Answer: If your question has been answered by a reply, mark the most helpful reply as the solution.

Note: This dormant notification will only apply to Discussions with the Question label. To learn more, see our recent announcement.

Thank you for helping bring this Discussion to a resolution! 💬

[jonathan-mothership]

We're seeing the same issue, there's no apparent way in on.issue_comment to get the name of the target branch. This blocks attempts to validate both source and target branch names in an action triggered by a comment.