add mutable shortlinks

this allows mapping cleanly from the existing mutable links on nixos.org

Author: fricklerhandwerk

default.nix

@@ -31,26 +31,36 @@ let
         # FIXME: This requires human interaction to update!
         # See ./CONTRIBUTING.md for details.
         # Using Nix from Nixpkgs could simplify handling, but would requires a bit more setup here
-        releases = [
-          "2.19"
-          "2.18"
-          "2.13"
-        ];
+        releases = {
+          latest = "2.19";
+          rolling = "2.18";
+          stable = "2.18";
+          prev-stable = "2.13";
+        };
         inputName = version: pkgs.lib.strings.replaceStrings [ "." ] [ "-" ] version;
         src = version: inputs."nix_${inputName version}";
         manual = version: (import (src version)).default.doc;
         copy = version: ''
           cp -Rf ${manual version}/share/doc/nix/manual/* $out/manual/nix/${version}
-          # use upstream page redirects
+        '';
+        redirects = version: ''
           sed 's#^\(.*\) \(.*\) #/manual/nix/${version}\1 /manual/nix/${version}\2 #g' ${src version}/doc/manual/_redirects >> $out/_redirects
         '';
+        shortlink = release: version: ''
+          echo /manual/nix/${release} /manual/nix/${version} >> $out/_redirects
+        '';
+        versions = with pkgs.lib; lists.unique (attrsets.attrValues releases);
       in
+      with pkgs.lib.attrsets;
       with pkgs.lib.strings;
       ''
+        mkdir -p $out
+        cp -R build/html/* $out/
         # NOTE: the comma in the shell expansion makes it also work for singleton lists
         mkdir -p $out/manual/nix/{${concatStringsSep "," releases},}
-        cp -R build/html/* $out/
-        ${concatStringsSep "\n" (map copy releases)}
+        ${concatStringsSep "\n" (map copy versions)}
+        ${concatStringsSep "\n" (map redirects versions)}
+        ${concatStringsSep "\n" (mapAttrsToList shortlink releases)}
       '';
   };