Update .github/workflows/ci.yml

Co-authored-by: Thomas Lively <7121787+tlively@users.noreply.github.com>
diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index c8ff7b9..f9cda21 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -108,7 +108,7 @@
     # XXX  run: python check.py --binaryen-bin=out/bin
 
     - name: verify auto-updating causes no changes
-      run: ./auto_update_tests.py lit | git diff test/
+      run: ./auto_update_tests.py lit | git diff -- test/
       if: matrix.os == 'ubuntu-latest'
 
   build-clang: