Add sprockets precompile rake task

Author: kinow

templates/project/Rakefile

@@ -0,0 +1,33 @@
+# First need to import Dashing with the Smashing Sinatra App
+require 'dashing'
+# Then import Sinatra, which will prepare sprockets settings
+require 'sinatra'
+# Now match the imports from Smashing's app.rb so that the resources are pre-processed
+require 'coffee-script'
+require 'sass' if RUBY_VERSION < "2.5.0"
+require 'sassc' if RUBY_VERSION >= "2.5.0"
+# Logger and misc
+require 'pathname'
+require 'logger'
+
+# From: https://simonecarletti.com/blog/2011/09/using-sprockets-without-a-railsrack-project/
+ROOT        = Pathname(File.dirname(__FILE__))
+LOGGER      = Logger.new(STDOUT)
+BUNDLES     = %w( application.js )
+BUILD_DIR   = ROOT.join("assets/javascripts/")
+
+# This contains the settings from the Smashign Sinatra App (see app.rb)
+# so no need to append_path, etc.
+sprockets = Sinatra::Application.settings.sprockets
+sprockets.logger = LOGGER
+
+# Task: precompile-assets
+# Pre-compiles sprockets application.js so users don't need to wait for Sinatra/Sprockets
+# to generate it on the fly.
+# see: https://github.com/Smashing/smashing/issues/189
+task :'precompile-assets' do
+  BUNDLES.each do |bundle|
+    asset = sprockets.find_asset(bundle)
+    asset.write_to(BUILD_DIR.join(asset.logical_path))
+  end
+end