Checkout forked code when running CI against pull requests

Author: FooBarWidget

.github/workflows/ci.yaml

@@ -23,8 +23,16 @@ jobs:
       BUNDLE_WITHOUT: lint
     steps:
       - name: Checkout code
+        if: github.event_name == 'push'
         uses: actions/checkout@v4
 
+      - name: Checkout PR code
+        if: github.event_name == 'pull_request_target'
+        uses: actions/checkout@v4
+        with:
+          ref: ${{ github.event.pull_request.head.ref }}
+          repository: ${{ github.event.pull_request.head.repo.full_name }}
+
       - name: Set up Ruby
         uses: ruby/setup-ruby@v1
         with:
@@ -41,8 +49,16 @@ jobs:
     runs-on: ubuntu-24.04
     steps:
       - name: Checkout code
+        if: github.event_name == 'push'
         uses: actions/checkout@v4
 
+      - name: Checkout PR code
+        if: github.event_name == 'pull_request_target'
+        uses: actions/checkout@v4
+        with:
+          ref: ${{ github.event.pull_request.head.ref }}
+          repository: ${{ github.event.pull_request.head.repo.full_name }}
+
       - name: Set up Ruby
         uses: ruby/setup-ruby@v1
         with: