anchor.diff:  
       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
  
positive.code: 
      deployment.adhoc.createVMCommand = mkOption {
        default = "create-vm";
        description = ''
          Remote command to create a NixOS virtual machine.  It should
          print an identifier denoting the VM on standard output.
  
negative.code: 
      deployment.adhoc.destroyVMCommand = mkOption {
        default = "destroy-vm";
        type = types.uniq types.string;
        description = ''
          Remote command to destroy a previously created NixOS virtual
          machine.
  