bug#20314: [PATCH] Make output of mdate-sh deterministic

[Paul Eggert]

Unfortunately that patch to Automake's mdate-sh is not portable, as TZ='UTC' is
not a portable setting for the TZ environment variable. POSIX says you're
supposed to use something like TZ='UTC0' instead. Although TZ='UTC' works when
glibc is used, this is not necessarily true on other POSIX platforms.

I noticed this problem when recent Automake changes were merged into Gnulib, and
installed the attached patch to the Automake master branch to fix this. Please
review any other patches you may be using for reproducible builds, and fix them
to use TZ='UTC0' instead of TZ='UTC'. Thanks.

For reference, here's the POSIX spec for TZ:

http://pubs.opengroup.org/onlinepubs/9699919799/basedefs/V1_chap08.html#tag_08_03

and look for "TZ".

[Mathieu Lirzin]

Hello Paul,

Post by Paul Eggert
Unfortunately that patch to Automake's mdate-sh is not portable, as
TZ='UTC' is not a portable setting for the TZ environment
variable. POSIX says you're supposed to use something like TZ='UTC0'
instead. Although TZ='UTC' works when glibc is used, this is not
necessarily true on other POSIX platforms.
I noticed this problem when recent Automake changes were merged into
Gnulib, and installed the attached patch to the Automake master branch
to fix this. Please review any other patches you may be using for
reproducible builds, and fix them to use TZ='UTC0' instead of
TZ='UTC'. Thanks.
http://pubs.opengroup.org/onlinepubs/9699919799/basedefs/V1_chap08.html#tag_08_03
and look for "TZ".

Thanks for fixing that and for the reference.

Post by Paul Eggert
From 5b240b3b36766045a47a6ad89ae5f4550e81d534 Mon Sep 17 00:00:00 2001
Date: Thu, 21 Sep 2017 20:08:48 -0700
Subject: [PATCH] * lib/mdate.sh (TZ): Use portable setting.

nitpick: I would prefer your future commit messages to include a summary
line before the list of modified files.