[gry]

$ bundle package

Places the gem binaries in vendor/cache, as noted. SCM those.

"While installing gems, Bundler will check vendor/cache and then your system's gems. If a gem isn't cached or installed, Bundler will try to install it from the sources you have declared in your Gemfile."

http://gembundler.com/bundle_install.html

Heroku uses this tree lookup AFAIK.

[timr]

Yeah, I knew that part...I wasn't sure what the default heroku ruby buildpack did. I'm still digging into the source to see what the build process is. It's non-trivial.

UPDATE:

For others' edification, the default heroku ruby buildpack respects vendor/cache, but will purge it in the following scenarios:

  * if vendor/ruby_version exists
  * if vendor/heroku/buildpack_version exists, but vendor/heroku/ruby_version does not
  * if the bundler cache exists, but vendor/heroku/ruby_version file specifies a different version of ruby than the one actually being used.