Actually save the m2m on the destination.

Author: pcraciunoiu

model_clone/mixin.py

@@ -719,6 +719,8 @@ def __duplicate_linked_m2m_fields(self, duplicate):
         :return: The duplicate instance objects from all the many-to-many fields duplicated.
         """
 
+        changed = False
+
         for field in self._meta.many_to_many:
             if all(
                 [
@@ -730,5 +732,9 @@ def __duplicate_linked_m2m_fields(self, duplicate):
                 source = getattr(self, field.attname)
                 destination = getattr(duplicate, field.attname)
                 destination.set(list(source.all()))
+                changed = True
+
+        if changed:
+            duplicate.save()
 
         return duplicate