Make commit fail if formatter fails

pre-commit

@@ -13,8 +13,11 @@ if hash black 2>/dev/null; then
 
     # Only run if we have cached python files
     if [ "$cached_files" ]; then 
-        black --line-length 100 $cached_files
-        git add $cached_files
+        black --line-length 100 $cached_files \
+     && git add $cached_files \
+     || exit 1
+
+     
     fi
 
 else
@@ -30,8 +33,9 @@ if hash idea.sh 2>/dev/null; then
 
 
     if [ "$cached_files" ]; then 
-        idea.sh format -allowDefaults $cached_files 2>/dev/null
-        git add $cached_files
+        idea.sh format -allowDefaults $cached_files 2>/dev/null \
+     && git add $cached_files \
+     || exit 1
     fi
 else
     echo "intellij isn't installed so not formatting java code"