Side load a gem that's not in Gemfile

add_gem_path.rb

module GemSideLoad
  class << self
    attr_accessor :last
  end
  module Gem
    VERSION = '1.0.0'
    Requirement = Struct.new(:wat)
    Version = Struct.new(:version)
    class Version
      def >=(other)
        self.version >= other.version
      end
    end
    class Specification < OpenStruct
      attr_reader :depends
      def initialize(&block)
        super
        @depends = []
         ::GemSideLoad.last = self
        yield self
      end
      def add_dependency(wat, *args)
        @depends << wat
      end
      def add_runtime_dependency(wat, *args)
        @depends << wat
      end
      def add_development_dependency(*_args)
      end
    end
  end
  def self.add(gem_name)
    return unless gem_name
    gems = ::Gem.default_path.last
    specs = gems + '/specifications'
    eval(File.read(specs + '/' + gem_name + '.gemspec'), binding)
    spec = GemSideLoad.last
    $:.push(*(dirs=Dir.glob("#{gems}/gems/#{gem_name}/{#{spec.require_paths.join(',')}}")))
    $:.uniq!
    GemSideLoad.last
  end
end
def add_gem_path(name)
  gems = Gem.default_path.last
  dir = Dir.entries(gems+'/gems').grep(/#{name}-[0-9]/).sort.last
  unless dir
    warn "#{name} not found in #{gems}/gems"
    return
  end
  spec = GemSideLoad.add(dir)
  spec.depends # auto-load deps?
end