GH1090 Fix comment commands not checking out the correct branch

.github/workflows/comment_commands.yml

@@ -21,23 +21,10 @@ jobs:
     if: (github.event.issue.pull_request) && contains(fromJSON('["/pandas_nightly", "/pyright_strict", "/mypy_nightly"]'), github.event.comment.body)
 
     steps:
-      - uses: actions/checkout@v4
-
-      - name: Install project dependencies
-        uses: ./.github/setup
-        with:
-          os: ubuntu-latest
-          python-version: "3.11"
-
-      - name: Run ${{ fromJSON(env.DISPLAY_COMMAND)[github.event.comment.body] }}
-        # run the tests based on the value of the comment
-        id: tests-step
-        run: poetry run poe ${{ fromJSON(env.RUN_COMMAND)[github.event.comment.body] }}
-
-      - name: Get head sha and store value
+      - name: Get head sha, branch name and store value
         # get the sha of the last commit to attach the results of the tests
         if: always()
-        id: get-sha
+        id: get-branch-info
         uses: actions/github-script@v7
         with:
           github-token: ${{ secrets.GITHUB_TOKEN }}
@@ -48,6 +35,25 @@ jobs:
               pull_number: ${{ github.event.issue.number }}
             })
             core.setOutput('sha', pr.data.head.sha)
+            core.setOutput('branch', pr.data.head.ref)
+
+      - name: Checkout code on the correct branch
+        uses: actions/checkout@v4
+        with:
+          # context is not aware which branch to checkout so it would otherwise
+          # default to main
+          ref: ${{ steps.get-branch-info.outputs.branch }}
+
+      - name: Install project dependencies
+        uses: ./.github/setup
+        with:
+          os: ubuntu-latest
+          python-version: "3.12"
+
+      - name: Run ${{ fromJSON(env.DISPLAY_COMMAND)[github.event.comment.body] }}
+        # run the tests based on the value of the comment
+        id: tests-step
+        run: poetry run poe ${{ fromJSON(env.RUN_COMMAND)[github.event.comment.body] }}
 
       - name: Report results of the tests and publish
         # publish the results to a check run no matter the pass or fail
@@ -58,7 +64,7 @@ jobs:
           script: |
             github.rest.checks.create({
               name: '${{ fromJSON(env.DISPLAY_COMMAND)[github.event.comment.body] }}',
-              head_sha: '${{ steps.get-sha.outputs.sha }}',
+              head_sha: '${{ steps.get-branch-info.outputs.sha }}',
               status: 'completed',
               conclusion: '${{ steps.tests-step.outcome }}',
               output: {