An example of a helper for determining which instance/flavor we're running.

application_helper.rb

  # A helper for determining which partner site we're on. This can be
  # used for setting a CSS class on the body tag in the layout, or 
  # for referencing namespaced assets or translations. 
  def parner(host=request.host)
    if $ENV['PARTNER'] == 'graduate' || host =~ /graduate/i
      'graduate'
    elsif $ENV['PARTNER'] == 'schreyer' || host =~ /schreyer/i
      'schreyer'
    else
      # decide whether to fail or default to one of the above
    end
  end

Although it is a little less slick than just being able to symlink and open http://schreyer.dev/ ...