Add config.action_controller.include_all_helpers, by default it is set to true.

In older rails versions there was a way to use only helpers from
helper file corresponding to current controller and you could also
include all helpers by saying 'helper :all' in controller. This config
allows to return to older behavior by setting it to false.

actionpack/lib/action_controller/metal/helpers.rb

@@ -53,8 +53,9 @@ module Helpers
     include AbstractController::Helpers
 
     included do
-      config_accessor :helpers_path
+      config_accessor :helpers_path, :include_all_helpers
       self.helpers_path ||= []
+      self.include_all_helpers = true
     end
 
     module ClassMethods

actionpack/lib/action_controller/railties/paths.rb

@@ -13,7 +13,9 @@ def self.with(app)
             end
 
             klass.helpers_path = paths
-            klass.helper :all if klass.superclass == ActionController::Base
+            if klass.superclass == ActionController::Base && ActionController::Base.include_all_helpers
+              klass.helper :all
+            end
           end
         end
       end

railties/test/application/initializers/frameworks_test.rb

@@ -65,6 +65,66 @@ def notify
       assert_equal ["notify"], Foo.action_methods
     end
 
+    test "allows to not load all helpers for controllers" do
+      add_to_config "config.action_controller.include_all_helpers = false"
+
+      app_file "app/controllers/application_controller.rb", <<-RUBY
+        class ApplicationController < ActionController::Base
+        end
+      RUBY
+
+      app_file "app/controllers/foo_controller.rb", <<-RUBY
+        class FooController < ApplicationController
+          def included_helpers
+            render :inline => "<%= from_app_helper -%> <%= from_foo_helper %>"
+          end
+
+          def not_included_helper
+            render :inline => "<%= respond_to?(:from_bar_helper) -%>"
+          end
+        end
+      RUBY
+
+      app_file "app/helpers/application_helper.rb", <<-RUBY
+        module ApplicationHelper
+          def from_app_helper
+            "from_app_helper"
+          end
+        end
+      RUBY
+
+      app_file "app/helpers/foo_helper.rb", <<-RUBY
+        module FooHelper
+          def from_foo_helper
+            "from_foo_helper"
+          end
+        end
+      RUBY
+
+      app_file "app/helpers/bar_helper.rb", <<-RUBY
+        module BarHelper
+          def from_bar_helper
+            "from_bar_helper"
+          end
+        end
+      RUBY
+
+      app_file "config/routes.rb", <<-RUBY
+        AppTemplate::Application.routes.draw do
+          match "/:controller(/:action)"
+        end
+      RUBY
+
+      require 'rack/test'
+      extend Rack::Test::Methods
+
+      get "/foo/included_helpers"
+      assert_equal "from_app_helper from_foo_helper", last_response.body
+
+      get "/foo/not_included_helper"
+      assert_equal "false", last_response.body
+    end
+
     # AD
     test "action_dispatch extensions are applied to ActionDispatch" do
       add_to_config "config.action_dispatch.tld_length = 2"