assetfile.rb

require 'bundler'
Bundler.setup(:assets)

require 'rake-pipeline-web-filters'

RequireFilter = Rake::Pipeline::Web::Filters::NeuterFilter
REQUIRE_REGEX = %r{//= require (.*)}

output 'public'
load_paths = ['app/assets/javascripts', 'vendor/assets/javascripts']
outfiles = ['foo.js', 'application.js']

input load_paths, '*.js' do
  outfiles.each do |outfile|
    match outfile do
      filter RequireFilter, outfile, :require_regexp => REQUIRE_REGEX
    end
  end
end

Cool. We'll probably have to subclass NeuterFilter to turn //= require_tree into a Dir.glob.

Ah, I passed over NeuterFilter when I was looking rake-pipeline yesterday. Totally wasn't clear (from the name, at least) how I can use it for dependencies. Ended up specifying a manually ordered list to concat.

It does feel a little hacky though - how does this, for instance resolve deps in a manner that doesn't include the same files twice? (might already do that, i'm just curious)

@wycats suggests using Rails.application.assets.paths in the Assetfile to get the benefits of Rails's engine awesomeness.

@shajith: yes, NeuterFilter adds dependencies to an ordered set.