push option decomposition up a bit more

I think we can find the original place where `action` is added to the
options hash now.

actionpack/lib/action_dispatch/routing/mapper.rb

@@ -61,7 +61,7 @@ class Mapping #:nodoc:
         attr_reader :requirements, :conditions, :defaults
         attr_reader :to, :default_controller, :default_action, :as, :anchor
 
-        def self.build(scope, set, path, as, controller, options)
+        def self.build(scope, set, path, as, controller, default_action, options)
           options = scope[:options].merge(options) if scope[:options]
 
           options.delete :only
@@ -72,8 +72,6 @@ def self.build(scope, set, path, as, controller, options)
 
           defaults = (scope[:defaults] || {}).dup
 
-          default_action     = options.delete(:action) || scope[:action]
-
           new scope, set, path, defaults, as, controller, default_action, options
         end
 
@@ -1593,7 +1591,9 @@ def add_route(action, controller, options) # :nodoc:
                  name_for_action(options.delete(:as), action)
                end
 
-          mapping = Mapping.build(@scope, @set, URI.parser.escape(path), as, controller, options)
+          default_action     = options.delete(:action) || @scope[:action]
+
+          mapping = Mapping.build(@scope, @set, URI.parser.escape(path), as, controller, default_action, options)
           app, conditions, requirements, defaults, as, anchor = mapping.to_route
           @set.add_route(app, conditions, requirements, defaults, as, anchor)
         end

actionpack/test/dispatch/mapper_test.rb

@@ -41,8 +41,8 @@ def test_initialize
       end
 
       def test_mapping_requirements
-        options = { :action => 'bar', :via => :get }
-        m = Mapper::Mapping.build({}, FakeSet.new, '/store/:name(*rest)', nil, 'foo', options)
+        options = { :via => :get }
+        m = Mapper::Mapping.build({}, FakeSet.new, '/store/:name(*rest)', nil, 'foo', 'bar', options)
         _, _, requirements, _ = m.to_route
         assert_equal(/.+?/, requirements[:rest])
       end