Allow Relation#merge to take a proc.

This was requested by DHH to allow creating of one's own custom
association macros.

For example:

    module Commentable
      def has_many_comments(extra)
        has_many :comments, -> { where(:foo).merge(extra) }
      end
    end

    class Post < ActiveRecord::Base
      extend Commentable
      has_many_comments -> { where(:bar) }
    end

1 files changed, 20 insertions, 0 deletions

diff --git a/activerecord/CHANGELOG.md b/activerecord/CHANGELOG.md
index c78e602af7..8356b49bec 100644
--- a/activerecord/CHANGELOG.md
+++ b/activerecord/CHANGELOG.md
@@ -1,5 +1,25 @@
 ## Rails 4.0.0 (unreleased) ##
 
+*   Allow Relation#merge to take a proc.
+
+    This was requested by DHH to allow creating of one's own custom
+    association macros.
+
+    For example:
+
+        module Commentable
+          def has_many_comments(extra)
+            has_many :comments, -> { where(:foo).merge(extra) }
+          end
+        end
+
+        class Post < ActiveRecord::Base
+          extend Commentable
+          has_many_comments -> { where(:bar) }
+        end
+
+    *Jon Leighton*
+
 *   Add CollectionProxy#scope
 
     This can be used to get a Relation from an association.