title: How to handle revisions to a Wiki with ActiveRecord?
body: <p>I have a model Article, that has_many Revisions.  Revisions have a variety of columns storing all the information about the Article.  The Article also belongs_to a current_revision, which is the primary key of the Revision that is currently selected.  Each Revision is never changed after being created.</p>
  
  <p>When a user goes to edit an Article, I want to display a form that shows all the fields that are in revisions, pre-populated with that information from the current_revision.  That's simple enough, but when the user goes to save, I want to compare each field to the value in the current_revision.  If all of the fields are the same, I want to do nothing and discard the form post.  However, if any of the fields are different, I want to create a new Revision instead of writing to the previous Revision.</p>
  
  <p>How can I detect whether any field has changed except by manually hard-coding a test for each field of the Revision?</p>