title: Rails 5 Upgrade: routes.rb file cleared out
body: <p>I am upgrading a Rails app from 4.2.x to 5.0.x. After I updated all my Rails-related gems in <code>Gemfile</code>, I ran the <code>rails</code> task for updating all my files to conform to the newest version, as per the <a href="http://edgeguides.rubyonrails.org/upgrading_ruby_on_rails.html" rel="noreferrer">upgrade guide</a>:</p>
  
  <pre><code>rails app:update
  </code></pre>
  
  <p>There were many <em>conflicts</em> in this command, so I pressed <code>a</code> to accept all conflicts and then review them manually before committing them. My main concern is what happened to the <code>config/routes.rb</code> file. Basically, the  entire contents of the file, save for the <code>Rails.application.routes.draw</code> block and a single comment about the DSL added to the end of the file, were kept. All routes that have been added to the app over the years were cleared out, not to be found in any other file.</p>
  
  <p>This issue doesn't block me, I'll simply checkout the file to bring it back to its former state. However, what especially concerns me is that an essential file was cleared out in what appears to be a <strong>normal situation</strong> for upgrading a Rails version. I'd like to see if anyone else has run into this issue, whether this is expected, what's going on. Comments from Rails maintainers are welcome. Thank you.</p>