Fix sprockets warnings

Fixes #2598

actionpack/lib/sprockets/assets.rake

@@ -13,17 +13,20 @@ namespace :assets do
       # Ensure that action view is loaded and the appropriate sprockets hooks get executed
       ActionView::Base
 
-      assets = Rails.application.config.assets.precompile
       # Always perform caching so that asset_path appends the timestamps to file references.
       Rails.application.config.action_controller.perform_caching = true
+
+      config = Rails.application.config
+      assets = config.assets.precompile.dup
+      assets << {:to => File.join(Rails.public_path, config.assets.prefix)}
       Rails.application.assets.precompile(*assets)
     end
   end
 
   desc "Remove compiled assets"
   task :clean => [:environment, 'tmp:cache:clear'] do
-    assets = Rails.application.config.assets
-    public_asset_path = Rails.public_path + assets.prefix
+    config = Rails.application.config
+    public_asset_path = File.join(Rails.public_path, config.assets.prefix)
     rm_rf public_asset_path, :secure => true
   end
 end

actionpack/lib/sprockets/helpers/rails_helper.rb

@@ -112,11 +112,22 @@ module Sprockets
           asset_environment[source]
         end
 
+        def digest_for(logical_path)
+          if asset = asset_environment[logical_path]
+            return asset.digest_path
+          end
+
+          logical_path
+        end
+
         def rewrite_asset_path(source, dir)
           if source[0] == ?/
             source
           else
-            asset_environment.path(source, performing_caching?, dir)
+            source = digest_for(source) if performing_caching?
+            source = File.join(dir, source)
+            source = "/#{url}" unless source =~ /^\//
+            source
           end
         end
 

actionpack/lib/sprockets/railtie.rb

@@ -18,9 +18,8 @@ module Sprockets
       require 'sprockets'
 
       app.assets = Sprockets::Environment.new(app.root.to_s) do |env|
-        env.static_root = File.join(app.root.join('public'), config.assets.prefix)
-        env.logger = ::Rails.logger
-        env.version = ::Rails.env + "#{'-' + config.assets.version if config.assets.version.present?}"
+        env.logger  = ::Rails.logger
+        env.version = ::Rails.env + "-#{config.assets.version}"
 
         if config.assets.cache_store != false
           env.cache = ActiveSupport::Cache.lookup_store(config.assets.cache_store) || ::Rails.cache