You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: assets.rb
    path of file: ./repos/nesta/lib/nesta/static
    
    the code of the file until where you have to start completion: require 'rake'

module Nesta
  module Static
    class Assets
      def initialize(build_dir, lo
    
      def copy_file_tree(source_dir, dest_dir)
        files_in_tree(source_dir).each do |file|
          target = File.join(dest_dir, file.sub(/^#{source_dir}\//, ''))
          task = Rake::FileTask.define_task(target => file) do
            target_dir = File.dirname(target)
            FileUtils.mkdir_p(target_dir) unless Dir.exist?(target_dir)
            FileUtils.cp(file, target_dir)
            log("Copied #{file} to #{target}")
          end
          task.invoke
        end
      end