How should I white label a Rails app?

whitelabeling.rb

class ApplicationController < ActionController::Base
  around_filter :set_white_label

  private

  def set_white_label
    subdomains = request.subdomains - RESERVED_SUBDOMAINS
    if subdomains.empty?
      yield
      return
    end

    # Obviously extract this out to work with any subdomain we want
    if subdomains.first == "mycompany"
      white_label_view_path = File.expand_path(File.join(RAILS_ROOT, 'app', 'white_labels', "mycompany"))
      prepend_view_path(white_label_view_path)
      yield
    end
  end
end

I like it. Does the prepend_view_path allow you to only override some view files or do you need to have a complete set in that directory structure?

Only the ones you want to override. The idea is that it looks for the file in the requested path, and if it can't find it, looks in the standard dir structure.