puppet-r10k used to allow you to do a little thing like so:

class { 'r10k':
  version => '3.1.1',
  sources => {
    'puppet' => {
      'remote'  => '<https://servername/control_repo.git>',
      'basedir' => "${::settings::codedir}/environments",
      'prefix'  => false,
    }
  },
  manage_modulepath => false,
}

and then just puppet apply <this file> and now r10k is set up.