containers promise type

bundle agent main
{
  vars:
    "folder"
      string => "/home/tom/cfengine-website/";
  git:
    "website-repo"
      destination => "$(folder)",
      repository => "https://github.com/cfengine/website";
  containers:
    "cfengine-website"
      state => "running",
      containerfile => "$(folder)/Containerfile",
      ip => "127.0.0.1",
      port => "80";
  hostnames:
    "cfengine.com"
      container => "cfengine-website";
}