Add support for mount RackApp, :at => "/sprockets" with a shorthand of mount Sprockets => "/sprockets".

This is different from the match syntax in that it cannot be used for controller/action and it does not 
assume an anchor at the end of the match. 

For instance, in the above example, if the client asked for "/sprockets/foo.js", the Sprockets app would
have a SCRIPT_NAME of "/sprockets" and PATH_INFO of "/foo.js".

actionpack/lib/action_dispatch/routing/mapper.rb

@@ -1,5 +1,3 @@
-require "active_support/core_ext/hash/except"
-
 module ActionDispatch
   module Routing
     class Mapper
@@ -38,7 +36,7 @@ module ActionDispatch
         end
 
         def to_route
-          [ app, conditions, requirements, defaults, @options[:as] ]
+          [ app, conditions, requirements, defaults, @options[:as], @options[:anchor] ]
         end
 
         private
@@ -66,7 +64,7 @@ module ActionDispatch
 
           # match "account/overview"
           def using_match_shorthand?(args, options)
-            args.present? && options.except(:via).empty? && !args.first.include?(':')
+            args.present? && options.except(:via, :anchor).empty? && !args.first.include?(':')
           end
 
           def normalize_path(path)
@@ -87,7 +85,7 @@ module ActionDispatch
           end
 
           def requirements
-            @requirements ||= (@options[:constraints] || {}).tap do |requirements|
+            @requirements ||= returning(@options[:constraints] || {}) do |requirements|
               requirements.reverse_merge!(@scope[:constraints]) if @scope[:constraints]
               @options.each { |k, v| requirements[k] = v if v.is_a?(Regexp) }
             end
@@ -176,7 +174,8 @@ module ActionDispatch
         end
 
         def match(*args)
-          @set.add_route(*Mapping.new(@set, @scope, args).to_route)
+          mapping = Mapping.new(@set, @scope, args).to_route
+          @set.add_route(*mapping)
           self
         end
       end
@@ -295,6 +294,7 @@ module ActionDispatch
           options = args.extract_options!
 
           options = (@scope[:options] || {}).merge(options)
+          options[:anchor] = true unless options.key?(:anchor)
 
           if @scope[:name_prefix] && !options[:as].blank?
             options[:as] = "#{@scope[:name_prefix]}_#{options[:as]}"
@@ -538,6 +538,21 @@ module ActionDispatch
           end
         end
 
+        def mount(app, options = nil)
+          if options
+            path = options.delete(:at)
+          else
+            options = app
+            app, path = options.find { |k, v| k.respond_to?(:call) }
+            options.delete(app) if app
+          end
+
+          raise "A rack application must be specified" unless path
+
+          match(path, options.merge(:to => app, :anchor => false))
+          self
+        end
+
         def match(*args)
           options = args.extract_options!
 

actionpack/lib/action_dispatch/routing/route.rb

@@ -4,7 +4,7 @@ module ActionDispatch
       attr_reader :app, :conditions, :defaults, :name
       attr_reader :path, :requirements
 
-      def initialize(app, conditions = {}, requirements = {}, defaults = {}, name = nil)
+      def initialize(app, conditions, requirements, defaults, name, anchor)
         @app = app
         @defaults = defaults
         @name = name
@@ -17,7 +17,7 @@ module ActionDispatch
 
         if path = conditions[:path_info]
           @path = path
-          conditions[:path_info] = ::Rack::Mount::Strexp.compile(path, requirements, SEPARATORS)
+          conditions[:path_info] = ::Rack::Mount::Strexp.compile(path, requirements, SEPARATORS, anchor)
         end
 
         @conditions = conditions.inject({}) { |h, (k, v)|

actionpack/lib/action_dispatch/routing/route_set.rb

@@ -293,8 +293,8 @@ module ActionDispatch
         routes.empty?
       end
 
-      def add_route(app, conditions = {}, requirements = {}, defaults = {}, name = nil)
-        route = Route.new(app, conditions, requirements, defaults, name)
+      def add_route(app, conditions = {}, requirements = {}, defaults = {}, name = nil, anchor = true)
+        route = Route.new(app, conditions, requirements, defaults, name, anchor)
         @set.add_route(*route)
         named_routes[name] = route if name
         routes << route

actionpack/test/dispatch/mount_test.rb

@@ -0,0 +1,36 @@
+require 'abstract_unit'
+
+class TestRoutingMount < ActionDispatch::IntegrationTest
+  SprocketsApp = lambda { |env|
+    [200, {"Content-Type" => "text/html"}, ["#{env["SCRIPT_NAME"]} -- #{env["PATH_INFO"]}"]]
+  }
+
+  Router = ActionDispatch::Routing::RouteSet.new
+  Router.draw do
+    mount SprocketsApp, :at => "/sprockets"
+    mount SprocketsApp => "/shorthand"
+
+    scope "/its_a" do
+      mount SprocketsApp, :at => "/sprocket"
+    end
+  end
+
+  def app
+    Router
+  end
+
+  def test_mounting_sets_script_name
+    get "/sprockets/omg"
+    assert_equal "/sprockets -- /omg", response.body
+  end
+
+  def test_mounting_works_with_scope
+    get "/its_a/sprocket/omg"
+    assert_equal "/its_a/sprocket -- /omg", response.body
+  end
+  
+  def test_mounting_with_shorthand
+    get "/shorthand/omg"
+    assert_equal "/shorthand -- /omg", response.body
+  end
+end