From 55483974885b1e98fc392c73da93bb90e9204c56 Mon Sep 17 00:00:00 2001
From: Eelco Dolstra <edolstra@gmail.com>
Date: Wed, 29 May 2019 21:28:33 +0200
Subject: [PATCH] make-tarball.nix: Derive version from lastModified instead of
 revCount

GitHub flakes don't provide revCount.
---
 pkgs/top-level/make-tarball.nix | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/pkgs/top-level/make-tarball.nix b/pkgs/top-level/make-tarball.nix
index 288971403f1a..7bb18e765f17 100644
--- a/pkgs/top-level/make-tarball.nix
+++ b/pkgs/top-level/make-tarball.nix
@@ -17,7 +17,10 @@ releaseTools.sourceTarball {
 
   inherit officialRelease;
   version = pkgs.lib.fileContents ../../.version;
-  versionSuffix = "pre${toString nixpkgs.revCount}.${nixpkgs.shortRev}";
+  versionSuffix = "pre${
+    if nixpkgs ? lastModified
+    then builtins.substring 0 8 nixpkgs.lastModified
+    else toString nixpkgs.revCount}.${nixpkgs.shortRev}";
 
   buildInputs = [ nix.out jq lib-tests ];