heroku-buildpack-ruby is utilized as the buildpack for detecting and building your Ruby applications.
You can view the README for a full list of configuration options available to the buildpack.
A ruby app is detected based on the existence of one of the following files at the root directory of your source code:
Gemfile Gemfile.lock Rakefile
You can configure the ruby version used at runtime by specifying a
Gemfile file at the root of your source code:
source "https://rubygems.org" ruby "2.5.1" # ...
Gemfileto an app’s repo alongside its source code.