Allow to checkout a different repo than your own

.github/workflows/build-reusable.yaml

@@ -31,6 +31,15 @@ on:
       maven-args:
         description: Additional Maven arguments
         type: string
+      ref:
+        description: The branch, tag or SHA to checkout
+        # When running on `pull_request_target` use the PR branch, not the target branch
+        default: ${{ github.event_name == 'pull_request_target' && github.head_ref || github.ref }}
+        type: string
+      repository:
+        description: GitHub repository name with owner
+        default: ${{ github.repository }}
+        type: string
       reproducibility-check-enabled:
         description: Runs a reproducibility check on the build
         default: true
@@ -64,8 +73,8 @@ jobs:
       - name: Checkout repository
         uses: actions/checkout@eef61447b9ff4aafe5dcd4e0bbf5d482be7e7871   # 4.2.1
         with:
-          # When running on `pull_request` use the PR branch, not the target branch
-          ref: ${{ github.event_name == 'pull_request_target' && github.head_ref || github.ref }}
+          repository: ${{ inputs.repository }}
+          ref: ${{ inputs.ref }}
 
       - name: Set up Java
         uses: actions/setup-java@b36c23c0d998641eff861008f374ee103c25ac73   # 4.4.0