heroku/heroku-buildpack-ruby — pull request #147 by hone (2013-09-13 23:28:02+00:00)
Title: store the rails 4 asset cache to improve asset pipeline performance

Speed up the Rails 4 asset pipeline by caching the Rails `tmp/cache/assets` directory so sprockets can only compile the diff. There's also code to make sure the cache doesn't grow unbounded since sprockets/rails does not clean up after itself currently. We've limited the assets cache to 50mb.