- `brew.rb` needed updated to fail unless on Ruby 2.3
- `brew update` should unset `HOMEBREW_RUBY_PATH` to ensure that this
doesn't "stick" on a Ruby 2.0 version after a portable Ruby has been
installed.
This is the (partially) documented public API for Homebrew.
The main class you should look at is the {Formula} class (and classes linked from there). That's the class that's used to create Homebrew formulae (i.e. package descriptions). Assume anything else you stumble upon is private.