Fix GitHub action.

Author: smolkaj

.github/workflows/google-rpc-status-synced.yml

@@ -10,9 +10,12 @@ jobs:
     - uses: actions/checkout@v5
     - run: ./proto/update_google_rpc_status.sh
     - run: |
-        if git diff --exit-code proto/google/rpc/status.proto; then
-          exit 0
+        DIFF=$(git diff proto/google/rpc/status.proto)
+        if [ -n "$DIFF" ]; then
+          echo "$DIFF"
+          echo ""
+          echo "ERROR: proto/google/rpc/status.proto is not synced with upstream."
+          echo "Please run ./proto/update_google_rpc_status.sh to fix it."
+          exit 1
         fi
-        echo "Error: google/rpc/status.proto is not synced with upstream."
-        echo "Please run `./proto/update_google_rpc_status.sh` to fix it."
-        exit 1
+        echo "SUCCESS: proto/google/rpc/status.proto is synced with upstream."