Reusing Guard tasks via Rake

assets.rake

# There are a couple minor quirks (see https://github.com/guard/guard/issues/118),
# but mostly this is delightfully straightforward:

require 'guard'

namespace :assets do
  desc 'Generate CSS from all source LESS files'
  task :less do
    Guard.setup
    Guard::Dsl.evaluate_guardfile(:guardfile => 'Guardfile', :group => ['frontend'])
    # Would be nice if these were in a hash keyed by name:
    less = Guard.guards.select { |g| g.is_a? Guard::Less }.first
    less.run_all
  end
end