cache included partial templates

lib/liquid/tags/include.rb

@@ -24,8 +24,7 @@ module Liquid
     end
     
     def render(context)
-      source = _read_template_from_file_system(context)
-      partial = Liquid::Template.parse(source)
+      partial = _load_cached_partial(context)
       variable = context[@variable_name || @template_name[1..-2]]
       
       context.stack do
@@ -46,6 +45,20 @@ module Liquid
     end
    
     private
+      def _load_cached_partial(context)
+        cached_partials = context.registers[:cached_partials] || {}
+        template_name = context[@template_name]
+
+        if cached = cached_partials[template_name]
+          return cached
+        end
+        source = _read_template_from_file_system(context)
+        partial = Liquid::Template.parse(source)
+        cached_partials[template_name] = partial
+        context.registers[:cached_partials] = cached_partials
+        partial
+      end
+
       def _read_template_from_file_system(context)
         file_system = context.registers[:file_system] || Liquid::Template.file_system