Don't clone associations [#4894 state:resolved]

Cloning an active record object should be shallow in that it should copy attributes but not associations. This was no longer true as a result of #3164.

Signed-off-by: José Valim <jose.valim@gmail.com>

activerecord/lib/active_record/base.rb

@@ -1433,6 +1433,7 @@ def initialize_copy(other)
         end
 
         clear_aggregation_cache
+        clear_association_cache
         @attributes_cache = {}
         @new_record = true
         ensure_proper_type

activerecord/test/cases/base_test.rb

@@ -1401,6 +1401,14 @@ def test_clone_with_aggregate_of_same_name_as_attribute
     assert_not_equal clone.id, dev.id
   end
 
+  def test_clone_does_not_clone_associations
+    author = authors(:david)
+    assert_not_equal [], author.posts
+
+    author_clone = author.clone
+    assert_equal [], author_clone.posts
+  end
+
   def test_clone_preserves_subtype
     clone = nil
     assert_nothing_raised { clone = Company.find(3).clone }