Fix Recursive Includes

Another very amusing 3-year old bug from the main Instiki Bug Tracker
(don't they ever fix anything?): the chunk-handling code was supposed
to prevent recursive [[!include ...]] statements. Alas, instead of
actually preventing them it would -- when it encountered a recursive
include -- churn away until Rails ran out of stack space.

Fixed.

lib/chunks/include.rb

@@ -10,12 +10,14 @@ require 'chunks/wiki'
 class Include < WikiChunk::WikiReference
 
   INCLUDE_PATTERN = /\[\[!include\s+([^\]\s][^\]]+?)\s*\]\]/i
+  @@included_by = []
   def self.pattern() INCLUDE_PATTERN end
 
   def initialize(match_data, content)
     super
     @page_name = match_data[1].strip
     rendering_mode = content.options[:mode] || :show
+    @@included_by.push(@content.page_name)
     @unmask_text = get_unmask_text_avoiding_recursion_loops(rendering_mode)
   end
 
@@ -23,25 +25,26 @@ class Include < WikiChunk::WikiReference
   
   def get_unmask_text_avoiding_recursion_loops(rendering_mode)
     if refpage      
+      if @@included_by.include?(refpage.page.name)
+        @content.delete_chunk(self)
+        @@included_by = []
+        return "<em>Recursive include detected: #{@content.page_name} &#x2192; #{@content.page_name}</em>\n"
+      end
       # TODO This way of instantiating a renderer is ugly.
       renderer = PageRenderer.new(refpage.current_revision)
-      if renderer.wiki_includes.include?(@content.page_name)
-        # this will break the recursion
-        @content.delete_chunk(self)
-        return "<em>Recursive include detected; #{@page_name} --> #{@content.page_name} " + 
-               "--> #{@page_name}</em>\n"
-      else
       included_content =
         case rendering_mode
           when :show then renderer.display_content
           when :publish then renderer.display_published
           when :export then renderer.display_content_for_export
-          else raise "Unsupported rendering mode #{@mode.inspect}"
+        else
+          raise "Unsupported rendering mode #{@mode.inspect}"
         end
       @content.merge_chunks(included_content)
+      @@included_by = []
       return included_content.pre_rendered
-      end
     else
+      @@included_by = []
       return "<em>Could not include #{@page_name}</em>\n"
     end
   end