heroku/heroku-buildpack-ruby — pull request #270 by nmistry (2014-05-28 08:36:03+00:00)
Title: allows setting RAILS/RACK env from environment variables.  re: #239

The buildpack essentially ignores the RAILS_ENV and RACK_ENV environment variable. This is probably not the best way to solve this, but it allows for specifying the RAILS_ENV at build time, and run time.

reference #239