ecwolf: add passthru.updateScript

Before this change, nixpkgs-update had to rely on on Repology in order
to determine if there was an ECWolf update. When it comes to ECWolf
updates, Repology is a tertiary source of information. This change
allows nixpkgs-update (and any other tools) to use debian.drdteam.org to
determine if there is an ECWolf update. When it comes to ECWolf updates,
debian.drdteam.org is a primary source of information.

pkgs/games/ecwolf/default.nix

@@ -12,6 +12,9 @@
 , SDL2_net
 , SDL2_mixer
 , gtk3
+, writers
+, python3Packages
+, nix-update
 }:
 
 stdenv.mkDerivation rec {
@@ -41,6 +44,33 @@ stdenv.mkDerivation rec {
     makeWrapper $out/{Applications/ecwolf.app/Contents/MacOS,bin}/ecwolf
   '';
 
+  passthru.updateScript = let
+    updateScriptPkg = writers.writePython3 "ecwolf_update_script" {
+      libraries = with python3Packages; [ debian-inspector requests ];
+    } ''
+      from os import execl
+      from sys import argv
+
+      from debian_inspector.debcon import get_paragraphs_data
+      from requests import get
+
+      # The debian.drdteam.org repo is a primary source of information. It’s
+      # run by Blzut3, the creator and primary developer of ECWolf. It’s also
+      # listed on ECWolf’s download page:
+      # <https://maniacsvault.net/ecwolf/download.php>.
+      url = 'https://debian.drdteam.org/dists/stable/multiverse/binary-amd64/Packages'  # noqa: E501
+      response = get(url)
+      packages = get_paragraphs_data(response.text)
+      for package in packages:
+          if package['package'] == 'ecwolf':
+              latest_version = package['version']
+              break
+      nix_update_path = argv[1]
+
+      execl(nix_update_path, nix_update_path, '--version', latest_version)
+    '';
+  in [ updateScriptPkg (lib.getExe nix-update) ];
+
   meta = with lib; {
     description = "Enhanched SDL-based port of Wolfenstein 3D for various platforms";
     homepage = "https://maniacsvault.net/ecwolf/";