Added queryset clone support and tests, thanks to hensom

Fixes #130

tests/queryset.py

@@ -1692,6 +1692,35 @@ class QuerySetTest(unittest.TestCase):
 
         Number.drop_collection()
 
+    def test_clone(self):
+        """Ensure that cloning clones complex querysets
+        """
+        class Number(Document):
+            n = IntField()
+
+        Number.drop_collection()
+
+        for i in xrange(1, 101):
+            t = Number(n=i)
+            t.save()
+
+        test = Number.objects
+        test2 = test.clone()
+        self.assertFalse(test == test2)
+        self.assertEqual(test.count(), test2.count())
+
+        test = test.filter(n__gt=11)
+        test2 = test.clone()
+        self.assertFalse(test == test2)
+        self.assertEqual(test.count(), test2.count())
+
+        test = test.limit(10)
+        test2 = test.clone()
+        self.assertFalse(test == test2)
+        self.assertEqual(test.count(), test2.count())
+
+        Number.drop_collection()
+
     def test_unset_reference(self):
         class Comment(Document):
             text = StringField()
@@ -1850,6 +1879,30 @@ class QTest(unittest.TestCase):
         for condition in conditions:
             self.assertTrue(condition in query['$or'])
 
+
+    def test_q_clone(self):
+
+        class TestDoc(Document):
+            x = IntField()
+
+        TestDoc.drop_collection()
+        for i in xrange(1, 101):
+            t = TestDoc(x=i)
+            t.save()
+
+        # Check normal cases work without an error
+        test = TestDoc.objects(Q(x__lt=7) & Q(x__gt=3))
+
+        self.assertEqual(test.count(), 3)
+
+        test2 = test.clone()
+        self.assertEqual(test2.count(), 3)
+        self.assertFalse(test2 == test)
+
+        test2.filter(x=6)
+        self.assertEqual(test2.count(), 1)
+        self.assertEqual(test.count(), 3)
+
 class QueryFieldListTest(unittest.TestCase):
     def test_empty(self):
         q = QueryFieldList()
@@ -1904,8 +1957,5 @@ class QueryFieldListTest(unittest.TestCase):
         self.assertEqual(q.as_dict(), {'x': True, 'y': True, 'b': True, 'c': True})
 
 
-
-
-
 if __name__ == '__main__':
     unittest.main()