From 61956fb14c7bce71934cb99df42db51bbd5aff86 Mon Sep 17 00:00:00 2001
From: Janneke Nieuwenhuizen <janneke@gnu.org>
Date: Sat, 9 Sep 2023 14:04:20 +0200
Subject: [PATCH] build: Generate reproducible doc/version.texi.

* build-aux/GNUmakefile.in (doc/version.texi): Use timestamp from git.
---
 build-aux/GNUmakefile.in | 12 ++++++++----
 1 file changed, 8 insertions(+), 4 deletions(-)

diff --git a/build-aux/GNUmakefile.in b/build-aux/GNUmakefile.in
index c5ede91e..b7bb7928 100644
--- a/build-aux/GNUmakefile.in
+++ b/build-aux/GNUmakefile.in
@@ -170,10 +170,14 @@ uninstall:
 
 doc/version.texi: ${srcdest}doc/mes.texi GNUmakefile
 	@mkdir -p $(@D)
-	(set `LANG= date -r $< +'%d %B %Y'`;\
-	echo "@set UPDATED $$1 $$2 $$3"; \
-	echo "@set UPDATED-MONTH $$2 $$3"; \
-	echo "@set EDITION $(VERSION)"; \
+	timestamp=$$({ git log --pretty=format:%ct -- $<	\
+		       || date +%s -r $<; }			\
+	               | sort -n -r | head -n 1);		\
+	dmy=$$(date --date="@$$timestamp" "+%-d %B %Y");	\
+	(set `LANG='						\
+	echo "@set UPDATED $$dmy";				\
+	echo "@set UPDATED-MONTH $$my";				\
+	echo "@set EDITION $(VERSION)";				\
 	echo "@set VERSION $(VERSION)") > $@
 
 doc: doc/version.texi