Merge pull request #75 from puppetlabs/maint-update_checkout_ref_mend

(maint) - Update checkout ref on mend pr trigger

.github/workflows/tooling_mend_ruby.yml

@@ -8,15 +8,30 @@ on:
 jobs:
 
   mend:
-    if: github.event.pull_request.head.repo.full_name == github.repository
     runs-on: "ubuntu-latest"
 
     steps:
+      # To access the mend secrets, we now need to trigger on pull_request_target event
+      # which by default runs in the context of the main branch, so we use this to retrieve
+      # the PR object and then checkout the merge commit sha
+      - name: "Retrieve PR"
+        if: github.event_name == 'pull_request'
+        uses: actions/github-script@v7
+        id: pr
+        with:
+          script: |
+            const { data: pullRequest } = await github.rest.pulls.get({
+              ...context.repo,
+              pull_number: context.payload.pull_request.number,
+            });
+            return pullRequest
 
       - name: "checkout"
         uses: "actions/checkout@v4"
         with:
           fetch-depth: 1
+          # If we are on a PR, checkout the merge commit sha, else checkout the main branch
+          ref: ${{ fromJSON(steps.pr.outputs.result).merge_commit_sha || 'refs/heads/main'}}
 
       - name: "setup ruby"
         uses: "ruby/setup-ruby@v1"