Make deep copy of application generators on engine initialization.

Otherwise nested hashes will be same objects for both application and engine,
which will result in overwriting each others values on changes.

railties/lib/rails/configuration.rb

@@ -1,5 +1,6 @@
 require 'active_support/deprecation'
 require 'active_support/ordered_options'
+require 'active_support/core_ext/hash/deep_dup'
 require 'rails/paths'
 require 'rails/rack'
 
@@ -51,6 +52,13 @@ module Rails
         @colorize_logging = true
       end
 
+      def initialize_copy(source)
+        @aliases = @aliases.deep_dup
+        @options = @options.deep_dup
+        @fallbacks = @fallbacks.deep_dup
+        @templates = @templates.dup
+      end
+
       def method_missing(method, *args)
         method = method.to_s.sub(/=$/, '').to_sym
 

railties/lib/rails/engine/configuration.rb

@@ -10,7 +10,7 @@ module Rails
       def initialize(root=nil)
         super()
         @root = root
-        @generators = app_generators
+        @generators = app_generators.dup
       end
 
       # Returns the middleware stack for the engine.

railties/test/railties/engine_test.rb

@@ -701,6 +701,9 @@ module RailtiesTest
       generators = Bukkits::Engine.config.generators.options[:rails]
       assert_equal :active_record, generators[:orm]
       assert_equal :rspec        , generators[:test_framework]
+
+      app_generators = Rails.application.config.generators.options[:rails]
+      assert_equal :test_unit    , app_generators[:test_framework]
     end
   end
 end