anchor.diff:      deployment.targetEnv = mkOption {
         default = "none";
         example = "ec2";
  +      type = types.uniq types.string;
         description = ''
           This option specifies the type of the environment in which the
           machine is to be deployed by
  
positive.code: 
      deployment.adhoc.destroyVMCommand = mkOption {
        default = "destroy-vm";
        description = ''
          Remote command to destroy a previously created NixOS virtual
          machine.
  
negative.code: 
      deployment.adhoc.queryVMCommand = mkOption {
        default = "query-vm";
        type = types.uniq types.string;
        description = ''
          Remote command to query information about a previously created
          NixOS virtual machine.  It should print the IPv6 address of
  