rails/rails — pull request #7628 by Pranas (2012-09-13 18:59:04+00:00)
Title: Allow passing block to deep_merge and deep_merge!

Hash#merge accepts block that you can use to customize how hash values are merged. This change makes merge and deep_merge compatible.

http://www.ruby-doc.org/core-1.9.3/Hash.html#method-i-merge