title: "Was dirty" plugin for ActiveRecord?
body: <p>I'm working on some code that uses a lot of after_save callbacks, and I remember seeing a plugin that allows the <code>model.changes</code> array to persist after a call to <code>save</code>.</p>
  
  <p>It would be a great help if I could just write <code>if body_did_change?</code> in my <code>after_save</code> calls, instead of having to hack together something with a <code>before_save</code> filter just to set a flag.</p>
  
  <p>I have written something like this myself before, but I'd prefer to use something supported and I swear I've seen this plugin before.</p>