From 88f36d2694840816f01ee1436867533669757437 Mon Sep 17 00:00:00 2001
From: Artturin <Artturin@artturin.com>
Date: Fri, 6 Jan 2023 22:19:06 +0200
Subject: [PATCH] gzip: make reproducible when GZIP_NO_TIMESTAMPS is set

the logic can be tested with

```
$ GZIP_NO_TIMESTAMPS=1 && echo "${GZIP_NO_TIMESTAMPS:+-n }"
-n
$ unset GZIP_NO_TIMESTAMPS && echo "${GZIP_NO_TIMESTAMPS:+-n }"

```
---
 pkgs/stdenv/generic/setup.sh            |  4 ++++
 pkgs/tools/compression/gzip/default.nix | 14 +++++++-------
 2 files changed, 11 insertions(+), 7 deletions(-)

diff --git a/pkgs/stdenv/generic/setup.sh b/pkgs/stdenv/generic/setup.sh
index c6cdb6c3df75..4047d8f4ea29 100644
--- a/pkgs/stdenv/generic/setup.sh
+++ b/pkgs/stdenv/generic/setup.sh
@@ -1348,6 +1348,10 @@ showPhaseFooter() {
 
 
 genericBuild() {
+    # variable used by our gzip wrapper to add -n.
+    # gzip is in common-path.nix and is added to nix-shell but we only want to change its behaviour in nix builds. do not move to a setupHook in gzip.
+    export GZIP_NO_TIMESTAMPS=1
+
     if [ -f "${buildCommandPath:-}" ]; then
         source "$buildCommandPath"
         return
diff --git a/pkgs/tools/compression/gzip/default.nix b/pkgs/tools/compression/gzip/default.nix
index 771188a98cd9..4aa52ff020f4 100644
--- a/pkgs/tools/compression/gzip/default.nix
+++ b/pkgs/tools/compression/gzip/default.nix
@@ -1,7 +1,7 @@
 { lib, stdenv
 , fetchurl
+, makeWrapper
 , xz
-, writeText
 }:
 
 # Note: this package is used for bootstrapping fetchurl, and thus
@@ -22,7 +22,7 @@ stdenv.mkDerivation rec {
 
   enableParallelBuilding = true;
 
-  nativeBuildInputs = [ xz.bin ];
+  nativeBuildInputs = [ xz.bin makeWrapper ];
 
   makeFlags = [
     "SHELL=/bin/sh"
@@ -40,12 +40,12 @@ stdenv.mkDerivation rec {
   preFixup = ''
     sed -i '1{;/#!\/bin\/sh/aPATH="'$out'/bin:$PATH"
     }' $out/bin/*
-  '';
-
-  # set GZIP env variable to "-n" to stop gzip from adding timestamps
+  ''
+  # run gzip with "-n" when $GZIP_NO_TIMESTAMPS (set by stdenv's setup.sh) is set to stop gzip from adding timestamps
   # to archive headers: https://github.com/NixOS/nixpkgs/issues/86348
-  setupHook = writeText "setup-hook" ''
-    export GZIP="-n"
+  + ''
+    wrapProgram $out/bin/gzip \
+      --add-flags "\''${GZIP_NO_TIMESTAMPS:+-n}"
   '';
 
   meta = {