Fixed #7154 -- Inherit all model managers from abstract base classes.

Also added documentation describing how manager inheritance works (and when
manager aren't inherited). Based on some patches from sebastian_noack and
emulbreh.


git-svn-id: http://code.djangoproject.com/svn/django/trunk@8851 bcc190cf-cafb-0310-a4f2-bffc1f526a37

django/db/models/options.py

@@ -44,6 +44,9 @@ class Options(object):
         self.abstract = False
         self.parents = SortedDict()
         self.duplicate_targets = {}
+        # Managers that have been inherited from abstract base classes. These
+        # are passed onto any children.
+        self.abstract_managers = []
 
     def contribute_to_class(self, cls, name):
         from django.db import connection