Makes requirejs work with CDN

Author: juwalter

app/helpers/requirejs_helper.rb

@@ -11,7 +11,10 @@ def _requirejs_data(name, &block)
     {}.tap do |data|
       if name
         name += ".js" unless name =~ /\.js$/
-        data['main'] = _javascript_path(name).sub(/\.js$/,'')
+        data['main'] = _javascript_path(name).
+                        sub(/\.js$/,'').
+                        sub(baseUrl(name), '').
+                        sub(/\A\//, '')
       end
 
       data.merge!(yield controller) if block_given?
@@ -54,6 +57,8 @@ def requirejs_include_tag(name=nil, &block)
           # and in the build_config.
           run_config['paths'] = paths
         end
+
+        run_config['baseUrl'] = baseUrl(name)
         html.concat <<-HTML
         <script>var require = #{run_config.to_json};</script>
         HTML
@@ -89,4 +94,11 @@ def _javascript_path(name)
       "/assets/#{name}"
     end
   end
+
+  def baseUrl(js_asset)
+    js_asset_path = javascript_path(js_asset)
+    uri = URI.parse(js_asset_path)
+    asset_host = uri.host && js_asset_path.sub(uri.request_uri, '')
+    [asset_host, Rails.application.config.assets.prefix].join
+  end
 end