git-machete: enable automatic updates via nix-update

pkgs/applications/version-management/git-and-tools/git-machete/default.nix

@@ -1,6 +1,8 @@
 { lib, buildPythonApplication, fetchPypi
 , installShellFiles, pbr
-, flake8, mock, pycodestyle, pylint, tox }:
+, flake8, mock, pycodestyle, pylint, tox
+, nix-update-script
+}:
 
 buildPythonApplication rec {
   pname = "git-machete";
@@ -23,6 +25,12 @@ buildPythonApplication rec {
       installShellCompletion --zsh --name _git-machete completion/git-machete.completion.zsh
   '';
 
+  passthru = {
+    updateScript = nix-update-script {
+      attrPath = pname;
+    };
+  };
+
   meta = with lib; {
     homepage = "https://github.com/VirtusLab/git-machete";
     description = "Git repository organizer and rebase/merge workflow automation tool";