title: Slow assets compilation in development mode
body: <p>I have a large rails app with hundreds of coffee script files.</p>
  
  <p>Sometimes when I make a tiny change in a coffeescript file or I switch the branch the whole assets are being precompiled and I have to wait a long time for load the page:</p>
  
  <pre><code>Started GET "/assets/application.js" for 127.0.0.1 at 2013-01-11 19:39:45 +0100
  Compiled sprockets/commonjs.js  (0ms)  (pid 18142)
  Compiled jquery.js  (2ms)  (pid 18142)
  Compiled jquery_ujs.js  (0ms)  (pid 18142)
  Compiled underscore.js  (0ms)  (pid 18142)
  Compiled backbone.js  (0ms)  (pid 18142)
  Compiled backbone_rails_sync.js  (0ms)  (pid 18142)
  Compiled handlebars.runtime.js  (0ms)  (pid 18142)
  Compiled moment.js  (0ms)  (pid 18142)
  ...and so on
  </code></pre>
  
  <p>I use the following assets configuration <code>config/development.rb</code>:</p>
  
  <pre><code># Do not compress assets
  config.assets.compress = false
  
  # Expands the lines which load the assets
  config.assets.debug = false
  </code></pre>
  
  <p>When I set <code>config.assets.debug = false</code> I have to wait quite long time for load hundreds of js files.
  The question is: how to find the golden mean? How to optimize assets configuration in the development mode for the large app?</p>