Only test format when it is wanted

.github/workflows/format.yml

@@ -3,6 +3,10 @@ name: Code formatting
 on:
   pull_request:
     branches: [ master, develop ]
+    paths:
+      - '**.cpp'
+      - '**.h'
+      - '!src/libs/**'
 
 jobs:
   test-format:

tests/test-format.sh

@@ -16,6 +16,7 @@ for file in $CHANGED_FILES
 do
   [ -e "$file" ] || continue
   case "$file" in
+  src/libs/*) continue ;;
   *.cpp|*.h)
     echo Checking "$file"
     clang-format -i "$file"