add debug git diff name only

.harness/firebase-deploy.yaml

@@ -21,6 +21,7 @@ spec:
             echo build.target = ${{ build.target }}
             echo build.before = ${{ build.before }}
             echo build.after = ${{ build.after }}
+            git --no-pager diff --name-only ${{ build.before }}..${{ build.after }}
       - name: dind
         type: background
         spec: