Adds child_pages macro for wiki pages (#528).

git-svn-id: http://redmine.rubyforge.org/svn/trunk@1699 e93f8b46-1217-0410-a6f0-8f06a7374b81

vendor/plugins/acts_as_tree/lib/active_record/acts/tree.rb

@@ -70,6 +70,13 @@ module ActiveRecord
           nodes
         end
 
+        # Returns list of descendants.
+        #
+        #   root.descendants # => [child1, subchild1, subchild2]
+        def descendants
+          children + children.collect(&:children).flatten
+        end
+
         # Returns the root node of the tree.
         def root
           node = self