nixos/cgit: add package option

nixos/modules/services/networking/cgit.nix

···
         options = {
           enable = mkEnableOption (mdDoc "cgit");
 
+          package = mkPackageOptionMD pkgs "cgit" {};
+
           nginx.virtualHost = mkOption {
             description = mdDoc "VirtualHost to serve cgit on, defaults to the attribute name.";
             type = types.str;
···
             [ "cgit.css" "cgit.png" "favicon.ico" "robots.txt" ]
             (name: nameValuePair "= ${stripLocation cfg}/${name}" {
               extraConfig = ''
-                alias ${pkgs.cgit}/cgit/${name};
+                alias ${cfg.package}/cgit/${name};
               '';
             })
         ) // {
···
           };
           "${stripLocation cfg}/" = {
             fastcgiParams = {
-              SCRIPT_FILENAME = "${pkgs.cgit}/cgit/cgit.cgi";
+              SCRIPT_FILENAME = "${cfg.package}/cgit/cgit.cgi";
               QUERY_STRING = "$args";
               HTTP_HOST = "$server_name";
               CGIT_CONFIG = mkCgitrc cfg;

nixos/tests/cgit.nix

···
-import ./make-test-python.nix ({ pkgs, ...} : {
+import ./make-test-python.nix ({ pkgs, ... }:
+let
+  robotsTxt = pkgs.writeText "cgit-robots.txt" ''
+    User-agent: *
+    Disallow: /
+  '';
+in {
   name = "cgit";
   meta = with pkgs.lib.maintainers; {
     maintainers = [ schnusch ];
···
     server = { ... }: {
       services.cgit."localhost" = {
         enable = true;
+        package = pkgs.cgit.overrideAttrs ({ postInstall, ... }: {
+          postInstall = ''
+            ${postInstall}
+            cp ${robotsTxt} "$out/cgit/robots.txt"
+          '';
+        });
         nginx.location = "/(c)git/";
         repos = {
           some-repo = {
···
     server.wait_for_unit("network.target")
     server.wait_for_open_port(80)
 
-    server.succeed("curl -fsS http://localhost/%28c%29git/robots.txt")
+    server.succeed("curl -fsS http://localhost/%28c%29git/cgit.css")
+
+    server.succeed("curl -fsS http://localhost/%28c%29git/robots.txt | diff -u - ${robotsTxt}")
 
     server.succeed(
         "curl -fsS http://localhost/%28c%29git/ | grep -F 'some-repo description'"