title: What's the "Rails way" to route a "diff" between two instances of the same model?
body: <p>I'm building a <a href="https://makelight.com/brand" rel="nofollow noreferrer">"Brand personality" tool</a> that gives you a report based on the text you share on social media. </p>
  
  <p>I have a model <code>PersonalityReport</code> and in routes I have <code>resources :personality_reports</code>.</p>
  
  <p>A new feature is to offer a "diff" between two reports and I'm trying to work out the most "guessable" way to model this in routes.</p>
  
  <p>Ideally I'd like <code>GET /personality_reports/:personality_report_id/diff/:id</code> or something along those lines, and while I could simply put that into routes as a GET route, is there a more Railsy way of specifying a route using the <code>resources</code> / <code>collections</code> style so that my <code>routes.rb</code> file is more easy to understand? </p>