Revert "Don't evaluate haskellPackages when gitit is disabled"

This reverts commit 99750d89dd962cc7011b02e487ed1a38c7842524.

nixos/modules/services/misc/gitit.nix

···
       };
 
       haskellPackages = mkOption {
+        default = pkgs.haskellPackages;
         defaultText = "pkgs.haskellPackages";
         example = literalExample "pkgs.haskell.packages.ghc784";
         description = "haskellPackages used to build gitit and plugins.";
···
 
       staticDir = mkOption {
         type = types.path;
+        default = gititShared + "/data/static";
         description = ''
           Specifies the path of the static directory (containing javascript,
           css, and images).  If it does not exist, gitit will create it and
···
 
       templatesDir = mkOption {
         type = types.path;
+        default = gititShared + "/data/templates";
         description = ''
           Specifies the path of the directory containing page templates.  If it
           does not exist, gitit will create it with default templates.  Users
···
 
       plugins = mkOption {
         type = with types; listOf str;
+        default = [ (gititShared + "/plugins/Dot.hs") ];
         description = ''
           Specifies a list of plugins to load. Plugins may be specified either
           by their path or by their module name. If the plugin name starts
···
   options.services.gitit = gititOptions;
 
   config = mkIf cfg.enable {
-
-    services.gitit = {
-      haskellPackages = mkDefault pkgs.haskellPackages;
-      staticDir = gititShared + "/data/static";
-      templatesDir = gititShared + "/data/templates";
-      plugins = [ ];
-    };
 
     users.extraUsers.gitit = {
       group = config.users.extraGroups.gitit.name;