diff --git a/actionpack/lib/action_controller/base.rb b/actionpack/lib/action_controller/base.rb
index 0c229fda8d..f62a5502b4 100755
--- a/actionpack/lib/action_controller/base.rb
+++ b/actionpack/lib/action_controller/base.rb
@@ -425,6 +425,15 @@ module ActionController #:nodoc:
       #
       #   url_for :controller => 'posts', :action => nil
       #      
+      # If you explicitly want to create a URL that's almost the same as the current URL, you can do so using the
+      # :overwrite_params options. Say for your posts you have different views for showing and printing them.
+      # Then, in the show view, you get the URL for the print view like this
+      #
+      #   url_for :overwrite_params => { :action => 'print' }
+      #
+      # This takes the current URL as is and only exchanges the action. In contrast, <tt>url_for :action => 'print'</tt>
+      # would have slashed-off the path components are the changed action.
+      #
       # Instead of passing an options hash, you can also pass a method reference in the form of a symbol. Consider this example:
       #
       #   class WeblogController < ActionController::Base
diff --git a/activesupport/lib/active_support/inflector.rb b/activesupport/lib/active_support/inflector.rb
index f5c92cf4d9..087c883b0b 100644
--- a/activesupport/lib/active_support/inflector.rb
+++ b/activesupport/lib/active_support/inflector.rb
@@ -134,8 +134,7 @@ module Inflector
   end
 
   def foreign_key(class_name, separate_class_name_and_id_with_underscore = true)
-    Inflector.underscore(Inflector.demodulize(class_name)) + 
-      (separate_class_name_and_id_with_underscore ? "_id" : "id")
+    underscore(demodulize(class_name)) + (separate_class_name_and_id_with_underscore ? "_id" : "id")
   end
 
   def constantize(camel_cased_word)