From 7cf93cdb9667e44b7fea2b3aa7c5cbf9f1205e50 Mon Sep 17 00:00:00 2001
From: Yueh-Shun Li <shamrocklee@posteo.net>
Date: Tue, 9 Dec 2025 22:55:00 +0800
Subject: [PATCH] fetchFromGitHub: use fetchgit when postCheckout not empty

---
 pkgs/build-support/fetchgithub/default.nix |  1 +
 pkgs/build-support/fetchgithub/tests.nix   | 11 +++++++++++
 2 files changed, 12 insertions(+)

diff --git a/pkgs/build-support/fetchgithub/default.nix b/pkgs/build-support/fetchgithub/default.nix
index a08f6d5de12b..288a10b95a4b 100644
--- a/pkgs/build-support/fetchgithub/default.nix
+++ b/pkgs/build-support/fetchgithub/default.nix
@@ -15,6 +15,7 @@ let
     fetchLFS = false;
     forceFetchGit = false;
     leaveDotGit = null;
+    postCheckout = "";
     rootDir = "";
     sparseCheckout = null;
   };
diff --git a/pkgs/build-support/fetchgithub/tests.nix b/pkgs/build-support/fetchgithub/tests.nix
index df24cfc44380..05f87cdf7564 100644
--- a/pkgs/build-support/fetchgithub/tests.nix
+++ b/pkgs/build-support/fetchgithub/tests.nix
@@ -16,6 +16,17 @@
     hash = "sha256-7DszvbCNTjpzGRmpIVAWXk20P0/XTrWZ79KSOGLrUWY=";
   };
 
+  describe-tag = testers.invalidateFetcherByDrvHash fetchFromGitHub {
+    name = "describe-tag-nix-source";
+    owner = "NixOS";
+    repo = "nix";
+    rev = "2.3.15";
+    hash = "sha256-y7l+46lVP2pzJwGON5qEV0EoxWofRoWAym5q9VXvpc8=";
+    postCheckout = ''
+      { git -C "$out" describe || echo "git describe failed"; } | tee "$out"/describe-output.txt
+    '';
+  };
+
   sparseCheckout = testers.invalidateFetcherByDrvHash fetchFromGitHub {
     name = "sparse-checkout-nix-source";
     owner = "NixOS";