Refactor handling of action normalization

Reference:
Bloody mess internals
http://gusiev.com/slides/rails_contribution/static/#40

actionpack/lib/action_dispatch/routing/route_set.rb

@@ -514,11 +514,12 @@ module ActionDispatch
           @recall      = recall.dup
           @set         = set
 
+          normalize_recall!
           normalize_options!
           normalize_controller_action_id!
           use_relative_controller!
           normalize_controller!
-          handle_nil_action!
+          normalize_action!
         end
 
         def controller
@@ -537,6 +538,11 @@ module ActionDispatch
           end
         end
 
+        # Set 'index' as default action for recall
+        def normalize_recall!
+          @recall[:action] ||= 'index'
+        end
+
         def normalize_options!
           # If an explicit :controller was given, always make :action explicit
           # too, so that action expiry works as expected for things like
@@ -552,8 +558,8 @@ module ActionDispatch
             options[:controller]   = options[:controller].to_s
           end
 
-          if options[:action]
-            options[:action] = options[:action].to_s
+          if options.key?(:action)
+            options[:action] = (options[:action] || 'index').to_s
           end
         end
 
@@ -563,8 +569,6 @@ module ActionDispatch
         # :controller, :action or :id is not found, don't pull any
         # more keys from the recall.
         def normalize_controller_action_id!
-          @recall[:action] ||= 'index' if current_controller
-
           use_recall_for(:controller) or return
           use_recall_for(:action) or return
           use_recall_for(:id)
@@ -586,13 +590,11 @@ module ActionDispatch
           @options[:controller] = controller.sub(%r{^/}, '') if controller
         end
 
-        # This handles the case of action: nil being explicitly passed.
-        # It is identical to action: "index"
-        def handle_nil_action!
-          if options.has_key?(:action) && options[:action].nil?
-            options[:action] = 'index'
+        # Move 'index' action from options to recall
+        def normalize_action!
+          if @options[:action] == 'index'
+            @recall[:action] = @options.delete(:action)
           end
-          recall[:action] = options.delete(:action) if options[:action] == 'index'
         end
 
         # Generates a path from routes, returns [path, params].