fix(code-style.sh): Warn on non-C files

Signed-off-by: Rahix <rahix@rahix.de>

tools/code-style.sh

@@ -12,7 +12,7 @@ if ! command -v python3 >/dev/null 2>&1; then
     exit 127
 fi
 
-if [ "$#" == 0 ]; then
+if [[ "$#" == 0 ]]; then
     echo "usage: $0 <source.c> ..."
     exit 1
 fi
@@ -20,7 +20,12 @@ fi
 script_dir="$(dirname "$0")"
 
 for source_file in "$@"; do
-    echo "Formatting $source_file ..."
-    clang-format -i "$source_file"
-    python3 "$script_dir/fix-multi-decl.py" "$source_file"
+    if [[ "$source_file" == *.c ]]; then
+        echo "Formatting $source_file ..."
+        clang-format -i "$source_file"
+        python3 "$script_dir/fix-multi-decl.py" "$source_file"
+    else
+        echo "Not a C file: $source_file" >&2
+        continue
+    fi
 done