r10k.rb

#!/opt/puppet/bin/ruby
require 'puppet'
require 'r10k/deployment/environment'

Puppet.parse_config

keyscan = `ssh-keyscan github.com 2>/dev/null`.split

FileUtils.mkdir_p('/root/.ssh/')
FileUtils.touch('/root/.ssh/known_hosts')
sshkey = Puppet::Resource.new('sshkey', keyscan[0], :parameters => {
  :ensure =>'present',
  :target => "/root/.ssh/known_hosts",
  :type   => keyscan[1],
  :key    => keyscan[2],
})
result, report = Puppet::Resource.indirection.save(sshkey)


environment = R10K::Environment::Git.new(
  Puppet[:environment],
  Puppet.settings[:environmentpath],
  Puppet[:environment],
  {
    :remote => Dir.pwd,
    :ref => Puppet[:environment],
  }
)

environment.sync

puppetfile = environment.puppetfile
puppetfile.load!

puppetfile.modules.each do |mod|
  mod.sync
end

More comments:

R10K::Deployment::Environment is deprecated. Use R10K::Environment::Git.new. The order of args was shuffled to be more sane, so make sure you check out https://github.com/puppetlabs/r10k/blob/master/lib/r10k/environment/git.rb#L26-L34

R10K::Environment::Git.new(
  Puppet[:environment],
  Dir.pwd,
  Puppet[:environment], # watch out for environment name normalization; it won't happen automatically here
  {
    :remote => 'git://github.com/blarghy/mcblarghBLARGH',
    :ref => 'WHARRBARGL',
  }
)