I tried this tip: https://github.com/thoughtbot/laptop/pull/14#issuecomment-3192270 .
On deploy I see
-----> Using RUBY_VERSION: ruby-1.9.3-p0
But my logs show the environment variable is not respected
INFO ruby 1.9.2 (2011-07-09) [x86_64-linux]
Hacky / experimental solutions accepted!
Edit: I am on the cedar stack.
Here's an update for everyone referencing this question... Heroku now allows you to specify your ruby version in your Gemfile, thanks to their addition to the latest version of bundler.
First run:
then add ruby '1.9.3' to your Gemfile as such.
The full release from Heroku with details is at http://blog.heroku.com/archives/2012/5/9/multiple_ruby_version_support_on_heroku/