If you rename a category, also rename the category definition topic.

app/models/category.rb

@@ -32,6 +32,7 @@ class Category < ActiveRecord::Base
   after_create :create_category_definition
   after_create :publish_categories_list
   after_destroy :publish_categories_list
+  after_update :rename_category_definition, if: :name_changed?
 
   has_one :category_search_data
   belongs_to :parent_category, class_name: 'Category'
@@ -331,6 +332,15 @@ SQL
     url << "/#{parent_category.slug}" if parent_category_id
     url << "/#{slug}"
   end
+
+  # If the name changes, try and update the category definition topic too if it's
+  # an exact match
+  def rename_category_definition
+    old_name = changed_attributes["name"]
+    if topic.title == I18n.t("category.topic_prefix", category: old_name)
+      topic.update_column(:title, I18n.t("category.topic_prefix", category: name))
+    end
+  end
 end
 
 # == Schema Information

spec/models/category_spec.rb

@@ -220,6 +220,12 @@ describe Category do
       @category.topics_year.should  == 0
     end
 
+    it "renames the definition when renamed" do
+      @category.update_attributes(name: 'Troutfishing')
+      @topic.reload
+      @topic.title.should =~ /Troutfishing/
+    end
+
     it "should not set its description topic to auto-close" do
       category = Fabricate(:category, name: 'Closing Topics', auto_close_hours: 1)
       category.topic.auto_close_at.should be_nil