Adding exist to cache api. It's a bad idea that is changed in Rails e…

…dge, but this is mirroring how it works in 3.0.1.

lib/interlock/action_controller.rb

@@ -225,7 +225,14 @@ def read_fragment(key, options = nil)
           raise e
         end      
       end
-
+
+      def fragment_exist?(key, options = nil)
+        return unless perform_caching
+
+        instrument_fragment_cache :exist_fragment?, key do
+          cache_store.exist?(key, options)
+        end
+      end 
     end
 
     # With Rails 2.1 action caching, we need to slip in our :expire param into the ActionCacheFilter options, so that when we 

lib/interlock/config.rb

@@ -129,6 +129,10 @@ def write(name, content, options = {})
               content, 
               options.is_a?(Hash) ? options[:ttl] : Interlock.config[:ttl] )
           end
+
+          def exist?(*args)
+            read(*args)
+          end
         end
       end