fix checkout

.github/workflows/build-project.yml

@@ -4,6 +4,11 @@ on:
   push:
   pull_request:
   workflow_dispatch:
+    inputs:
+      checkout-ref:
+        description: "The branch, tag or SHA to checkout. See actions/checkout 'ref'."
+        required: false
+        type: string
 
 concurrency:
   group: "Build Project: ${{ github.workflow }} @ ${{ github.event.pull_request.head.label || github.head_ref || github.ref }}"
@@ -14,6 +19,11 @@ jobs:
   validate-gradle-wrapper:
     runs-on: ubuntu-latest
     steps:
+      - name: Checkout the repo
+        uses: actions/checkout@v4
+        with:
+          ref: ${{ inputs.checkout-ref || github.ref }}
+
       - name: Validate Gradle Wrapper
         uses: gradle/actions/wrapper-validation@v3
 
@@ -30,7 +40,7 @@ jobs:
       - name: Checkout the repo
         uses: actions/checkout@v4
         with:
-          ref: ${{ github.event.inputs.ref }}
+          ref: ${{ inputs.checkout-ref || github.ref }}
 
       - name: Setup JDK
         uses: actions/setup-java@v4