case ENV['DB']
  when "mysql"; gem "mysql2"
  when "sqlite"; gem "sqlite3" 
  when "postgresql"; gem "pg"
end

def gem(*args)
  # Override 'gem' method to block any other database gems in the 'real' Gemfile
  super unless %w(pg sqlite3 mysql2).include?(args.first)
end

# Eval Gemfile
eval(IO.read(File.join(File.dirname(__FILE__), 'Gemfile')), binding)