anchor.diff:          type = types.lines;
           default = "";
           example = ''
  -          gc-keep-outputs = true
  -          gc-keep-derivations = true
  +          keep-outputs = true
  +          keep-derivations = true
           '';
           description = "Additional text appended to <filename>nix.conf</filename>.";
         };
  
positive.code:             allowed-users = mkOption {
                type = types.listOf types.str;
                default = [ "*" ];
                example = [ "@wheel" "@builders" "alice" "bob" ];
                description = ''
                  A list of names of users (separated by whitespace) that are
                  allowed to connect to the Nix daemon. As with
  
negative.code:             trusted-users = mkOption {
                type = types.listOf types.str;
                default = [ "root" ];
                example = [ "root" "alice" "@admin" ];
                description = ''
                  A list of names of users that have additional rights when
                  connecting to the Nix daemon, such as the ability to specify
                  additional binary caches, or to import unsigned NARs. You
                  can also specify groups by prefixing them with
                  <literal>@</literal>; for instance,
                  <literal>@admin</literal> means all users in the wheel
                  group.
                '';
              };
  