RVM Cloud Native Buildpack

The RVM Cloud Native Buildpack installs RVM and a Ruby version in an OCI image. It has been created for usage in conjunction with the Rails builder.

Functionality

1. The RVM CNB installs RVM into its own layer. The version of RVM to be installed can be configured in buildpack.toml.
2. The files Gemfile and Gemfile.lock must exist in the application directory so that the RVM CNB can start the DETECTION phase.
3. It also installs a version of Ruby using RVM. The version to be installed is selected as follows (in order of precedence, the method listed highest wins):
   1. If there is a called buildpack.yml in the application directory, it may specify a ruby version. See below to learn possible keys in the buildpack.yml file.
   2. If there is a file called Gemfile.lock, then the string "RUBY VERSION" is searched within this file and if it exists, the contents of the next line is used to select the Ruby version.
   3. If there is a file called Gemfile, then the string "ruby <version string>" is searched within this file and if it exists, the given Ruby version is selected.
   4. If there is a .ruby-version file, its contents are used to select the Ruby version.
   5. If none of the files specified above exists, then the Ruby version specified in buildpack.toml will be selected. The variable that specifies the default Ruby version is called default_ruby_version.

buildpack.yml

A buildpack.yml may specify the following keys. If buildpack.yml specifies a Ruby version, it will have priority over all other Ruby version sources.

rvm:
  rvm_version: 1.29.10
  ruby_version: 2.6.1
  node_version: 10.*
  require_node: true

Dependencies

This CNB installs the Node CNB as a dependency in the build and launch layers. Currently, the default version of Node installed is the latest 12.* version.

TODO

1. Refactor this CNB and remove Bundler specific functionality
2. Only leave functionality directly related to the installation or configuration of RVM and a particular Ruby version