middleman/middleman-more/lib/middleman-more/extensions/relative_assets.rb

# Extension namespace
module Middleman
  module Extensions
  
    # Relative Assets extension
    module RelativeAssets
    
      # Setup extension
      class << self
      
        # Once registered
        def registered(app)
          # Tell compass to use relative assets
          app.compass_config do |config|
            config.relative_assets = true
          end
      
          # Include instance methods
          app.send :include, InstanceMethods
        end
      
        alias :included :registered
      end
  
      # Relative Assets instance method
      module InstanceMethods
      
        # asset_url override for relative assets
        # @param [String] path
        # @param [String] prefix
        # @return [String]
        def asset_url(path, prefix="")
          path = super(path, prefix)

          if path.include?("//")
            path
          else
            current_dir = Pathname('/' + current_resource.destination_path).dirname
            Pathname(path).relative_path_from(current_dir)
          end
        end
      end
    end
  end
end