module Hashie::Extensions::DeepMerge

def deep_merge(other_hash)
  (class << (h = dup); self; end).send :include, Hashie::Extensions::DeepMerge
  h.deep_merge!(other_hash)
end

def deep_merge!(other_hash)
  other_hash.each do |k,v|
    (class << (tv = self[k]); self; end).send :include, Hashie::Extensions::DeepMerge
    self[k] = tv.is_a?(::Hash) && v.is_a?(::Hash) ? tv.deep_merge(v) : v
  end
  self
end