namespace :dev do
  task :cache do
    desc 'Toggle development mode caching on/off'

    if File.exist? 'tmp/caching-dev.txt'
      File.delete 'tmp/caching-dev.txt'
      puts 'Development mode is no longer being cached.'
    else
      FileUtils.touch 'tmp/caching-dev.txt'
      puts 'Development mode is now being cached.'
    end

    FileUtils.touch 'tmp/restart.txt'
  end
end

namespace :dev do
  desc 'Toggle development mode caching on/off'
  task :cache do
    if File.exist? 'tmp/caching-dev.txt'
      File.delete 'tmp/caching-dev.txt'
      puts 'Development mode is no longer being cached.'
    else
      FileUtils.touch 'tmp/caching-dev.txt'
      puts 'Development mode is now being cached.'
    end

    FileUtils.touch 'tmp/restart.txt'
  end
end

Move the desc one level up
Move the desc one level up 

Make the task visible (from rake -T) by moving the desc one level up