Use already_notified in get_all_groups

wiki_groups/models.py

@@ -70,14 +70,20 @@ class WikiGroup(models.Model):
 
         return False
 
-    def get_all_groups(self):
+    def get_all_groups(self, already_notified=None):
         """Returns the set of metagroups i.e. self plus the list of groups including
         this group recursively"""
 
+        if already_notified is None:
+            already_notified = set()
+        elif self.pk in already_notified:
+            return set()
+        already_notified.add(self.pk)
+
         groups = {self}
 
         for metagroup in self.included_in_groups.all():
-            groups |= metagroup.get_all_groups()
+            groups |= metagroup.get_all_groups(already_notified=already_notified)
 
         return groups