title: Unexpected Behavior of 'config.assets.prefix' in Rails 4
body: <p>I have set the following configuration variable in <code>config/environments/development.rb</code>:</p>
  
  <pre><code>config.assets.prefix = "/dev-assets"
  </code></pre>
  
  <p>In Rails 3, this would have meant that in development, my application would look for assets in  <code>public/dev-assets</code>, rather than <code>public/assets</code> to avoid the risk of loading precompiled assets that might be present.</p>
  
  <p>However in Rails 4, setting this parameter and running <code>rake assets:precompile</code> now adds precompiled assets to <code>public/dev-assets</code>.</p>
  
  <p>It seems like this prefix is being used for both where Rails places precompiled assets AND where rails looks for assets. This means Rails will always pull assets from the same location it places precompiled assets, meaning potentially stale precompiled assets obscure the most current assets.</p>
  
  <p><strong>So how do I achieve the same thing in Rails 4? How can I precompile my assets to a different directory than the one rails looks for assets in?</strong></p>
  
  <p>Console output from <code>rake assets:precompile</code>:</p>
  
  <p><code>
  [2014-01-23T11:48:35.766582 #4234]  INFO -- : Writing /path/to/app/public/dev-assets/application-1b403217ee27653d8d1299aeb242462b.js
  I, [2014-01-23T11:48:35.819090 #4234]  INFO -- : Writing /path/to/app/public/dev-assets/application-8e258453df56d80e1a8b9b8a8e6f8db4.css
  </code></p>