Note on merge request open/close

app/models/mailer_observer.rb

@@ -59,6 +59,13 @@ class MailerObserver < ActiveRecord::Observer
         Notify.changed_merge_request_email(user, merge_request).deliver
       end
     end
+
+    if merge_request.closed_changed?
+      note = Note.new(:noteable => merge_request, :project => merge_request.project)
+      note.author = current_user
+      note.note = "_Status changed to #{merge_request.closed ? 'closed' : 'reopened'}_"
+      note.save()
+    end
   end
 
   def changed_issue(issue)