[bug#70169] [PATCH v3 09/13] maint: Use reproducible Git timestamp for POT-Creation-Date.

[Janneke Nieuwenhuizen]

* po/doc/local.mk (%D%/%.pot): Replace POT-Creation-Date using timestamp from
Git.
(%D%/guix-manual.pot): Likewise.

Change-Id: I1b7f8cc147084c1804deb7be9d36e5eeda2599cb
---
 po/doc/local.mk | 16 ++++++++++++----
 1 file changed, 12 insertions(+), 4 deletions(-)

diff --git a/po/doc/local.mk b/po/doc/local.mk
index dd6ba30133..77ec4721e3 100644
--- a/po/doc/local.mk
+++ b/po/doc/local.mk
@@ -1,6 +1,7 @@
 # GNU Guix --- Functional package management for GNU
 # Copyright © 2018 Julien Lepiller <julien@lepiller.eu>
 # Copyright © 2021 Maxim Cournoyer <maxim.cournoyer@gmail.com>
+# Copyright © 2024 Janneke Nieuwenhuizen <janneke@gnu.org>
 #
 # This file is part of GNU Guix.
 #
@@ -44,12 +45,19 @@ POT_OPTIONS = \
        --msgid-bugs-address "bug-guix@gnu.org"
 
 %D%/%.pot: $(srcdir)/doc/%.texi
-       $(AM_V_PO4A)$(PO4A_UPDATEPO) -M UTF-8 -f texinfo -m "$<" \
-          -p "$@" $(POT_OPTIONS) && \
-       touch $@
+       $(AM_V_PO4A)$(PO4A_UPDATEPO) -M UTF-8 -f texinfo -m "$<"        \
+          -p "$@-t" $(POT_OPTIONS)
+       date="$$(git log --pretty=format:%ci -n 1 -- $< 2>/dev/null     \
+               || echo $(SOURCE_DATE_EPOCH))"                          \
+       sed -ri -e "s,^(.POT-Creation-Date: )[^\]*,\1$$date," "$@-t"
+       mv "$@-t" "$@"
 
 %D%/guix-manual.pot: %D%/guix.pot %D%/contributing.pot
-       msgcat $^ > $@
+       msgcat $^ > "$@-t"
+       date="$$(git log --pretty=format:%ci -n 1 -- $< 2>/dev/null     \
+               || echo $(SOURCE_DATE_EPOCH))"                          \
+       sed -ri "s,^(.POT-Creation-Date: )[^\]*,\1$$date," "$@-t"
+       mv "$@-t" "$@"
 
 doc-pot-update: %D%/guix-manual.pot %D%/guix-cookbook.pot
 .PHONY: doc-pot-update
-- 
2.41.0