try to force xargs parallel

Author: hjwp

.github/workflows/tests.yml

@@ -52,12 +52,12 @@ jobs:
             --mount type=volume,source=rootmount,target=/root \
             --mount type=bind,source=./,target=/app \
             -t hjwp/obeythetestinggoat-book-tester:latest \
-            bash -c 'git submodule status | cut -d" " -f3 | xargs -I% bash -c "echo %"'
+            bash -c 'git submodule status | cut -d" " -f3 | xargs -P0 -I% bash -c "echo %"'
           docker run --rm \
             --mount type=volume,source=rootmount,target=/root \
             --mount type=bind,source=./,target=/app \
             -t hjwp/obeythetestinggoat-book-tester:latest \
-            bash -c 'git submodule status | cut -d" " -f3 | xargs -I% bash -c "cd % && git fetch"'
+            bash -c 'git submodule status | cut -d" " -f3 | xargs -P0 -I% bash -c "cd % && git fetch"'
 
       - name: check submodule branches
         run: |