nixVersions.nix_2_13: init at 2.13.1

https://github.com/NixOS/nix/releases/tag/2.13.0
https://github.com/NixOS/nix/releases/tag/2.13.1

pkgs/tools/package-management/nix/common.nix

@@ -11,6 +11,7 @@ let
   atLeast25 = lib.versionAtLeast version "2.5pre";
   atLeast27 = lib.versionAtLeast version "2.7pre";
   atLeast210 = lib.versionAtLeast version "2.10pre";
+  atLeast213 = lib.versionAtLeast version "2.13pre";
 in
 { stdenv
 , autoconf-archive
@@ -37,6 +38,7 @@ in
 , libsodium
 , lowdown
 , mdbook
+, mdbook-linkcheck
 , nlohmann_json
 , openssl
 , perl
@@ -83,6 +85,8 @@ self = stdenv.mkDerivation {
   ] ++ lib.optionals (atLeast24 && enableDocumentation) [
     (lib.getBin lowdown)
     mdbook
+  ] ++ lib.optionals (atLeast213 && enableDocumentation) [
+    mdbook-linkcheck
   ] ++ lib.optionals stdenv.isLinux [
     util-linuxMinimal
   ];

pkgs/tools/package-management/nix/default.nix

@@ -106,6 +106,11 @@ in lib.makeExtensible (self: {
     ];
   };
 
+  nix_2_13 = common {
+    version = "2.13.1";
+    sha256 = "sha256-uXh4+xjJUHQSCg+LHh6+SSYtMdjKQiTXMZ4uZFwzdq4=";
+  };
+
   stable = self.nix_2_12;
 
   unstable = self.stable;