Get the default branch of the repository to compare with.

Author: llrs-roche

.github/workflows/build-check-install.yaml

@@ -515,6 +515,14 @@ jobs:
           path: "${{ inputs.additional-caches }}"
           key: additional-caches-${{ runner.os }}
 
+      - name: Checkout default branch (PR) ⚙️
+        uses: actions/[email protected]
+        if: github.event_name == 'pull_request'
+        with:
+          path: ${{ github.event.repository.name }}
+          repository: ${{ github.event.pull_request.head.repo.full_name }}
+          fetch-depth: 1
+
       - name: Check only affected modules 🎯
         if: startsWith(${{ github.event.repository.name }}, "teal.modules.") && github.event_name == 'pull_request'
         run: |