From b114fecfe4ac817d780205a21424610ea600907b Mon Sep 17 00:00:00 2001
From: Malcolm Tredinnick <malcolm.tredinnick@gmail.com>
Date: Wed, 16 Apr 2008 08:09:18 +0000
Subject: [PATCH] queryset-refactor: Fixed a few inadvertent sharing problems
 for related fields in abstract base classes. This means, for example, that
 many-to-many fields can be used in abstract base classes.

git-svn-id: http://code.djangoproject.com/svn/django/branches/queryset-refactor@7431 bcc190cf-cafb-0310-a4f2-bffc1f526a37
---
 django/db/models/base.py            |  3 ++-
 django/db/models/fields/__init__.py | 13 ++++++++-----
 2 files changed, 10 insertions(+), 6 deletions(-)

diff --git a/django/db/models/base.py b/django/db/models/base.py
index 6fad7070ba..40af8a0ed9 100644
--- a/django/db/models/base.py
+++ b/django/db/models/base.py
@@ -1,3 +1,4 @@
+import copy
 import types
 import sys
 import os
@@ -111,7 +112,7 @@ class ModelBase(type):
                     if field.name in names:
                         raise FieldError('Local field %r in class %r clashes with field of similar name from abstract base class %r'
                                 % (field.name, name, base.__name__))
-                    new_class.add_to_class(field.name, field)
+                    new_class.add_to_class(field.name, copy.deepcopy(field))
 
         if abstract:
             # Abstract base models can't be instantiated and don't appear in
diff --git a/django/db/models/fields/__init__.py b/django/db/models/fields/__init__.py
index 6e426318f5..7778117fb3 100644
--- a/django/db/models/fields/__init__.py
+++ b/django/db/models/fields/__init__.py
@@ -1,3 +1,4 @@
+import copy
 import datetime
 import os
 import time
@@ -126,11 +127,13 @@ class Field(object):
         return cmp(self.creation_counter, other.creation_counter)
 
     def __deepcopy__(self, memodict):
-        # Slight hack; deepcopy() is difficult to do on classes with
-        # dynamically created methods. Fortunately, we can get away with doing
-        # a shallow copy in this particular case.
-        import copy
-        return copy.copy(self)
+        # We don't have to deepcopy very much here, since most things are not
+        # intended to be altered after initial creation.
+        obj = copy.copy(self)
+        if self.rel:
+            obj.rel = copy.copy(self.rel)
+        memodict[id(self)] = obj
+        return obj
 
     def to_python(self, value):
         """