FIX: don't validate topic title if it isn't changing. topic stats were failing to update, causing necro topic warnings and other problems.

app/models/topic.rb

@@ -48,7 +48,8 @@ class Topic < ActiveRecord::Base
   rate_limit :limit_topics_per_day
   rate_limit :limit_private_messages_per_day
 
-  validates :title, :presence => true,
+  validates :title, :if => Proc.new { |t| t.title_changed? },
+                    :presence => true,
                     :topic_title_length => true,
                     :quality_title => { :unless => :private_message? },
                     :unique_among  => { :unless => Proc.new { |t| (SiteSetting.allow_duplicate_topic_titles? || t.private_message?) },

spec/models/topic_spec.rb

@@ -1411,4 +1411,14 @@ describe Topic do
     topic = Topic.find(topic.id)
     topic.custom_fields.should == {"bob" => "marley", "jack" => "black"}
   end
+
+  it "doesn't validate the title again if it isn't changing" do
+    SiteSetting.stubs(:min_topic_title_length).returns(5)
+    topic = Fabricate(:topic, title: "Short")
+    topic.should be_valid
+
+    SiteSetting.stubs(:min_topic_title_length).returns(15)
+    topic.last_posted_at = 1.minute.ago
+    topic.save.should == true
+  end
 end