[PATCH v2] t9604: Fix test for musl libc and new Debian

CST6CDT and the like are POSIX timezone, with no rule for transition. And POSIX doesn't enforce how to interpret the rule if it's omited. Some libc (e.g. glibc) resorted back to IANA (formerly Olson) db rules for those timezones. Some libc (e.g. FreeBSD) uses a fixed rule. Other libc (e.g. musl) interpret that as no transition at all [1].

In addition, distributions (notoriously Debian-derived, which uses IANA db for CST6CDT and the like) started to split "legacy" timezones like CST6CDT, EST5EDT into `tzdata-legacy', which will not be installed by default [2].

In those cases, t9604 will run into failure.

Let's switch to POSIX timezone with rules to change timezone.

1: http://mm.icann.org/pipermail/tz/2024-March/058751.html 2: https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=1043250

Signed-off-by: Đoàn Trần Công Danh <congdanhqx@gmail.com>
---
Range-diff against v1:
1:  23a4298eababe ! 1:  9494adb39120c t9604: Fix test for musl libc and new Debian
    @@ Commit message
     
         CST6CDT and the like are POSIX timezone, with no rule for transition.
         And POSIX doesn't enforce how to interpret the rule if it's omited.
    -    Some libc resorted back to IANA (formerly Olson) db rules for those
    -    timezones.  Other libc (e.g. musl) interpret that as no transition at
    -    all [1].
    +    Some libc (e.g. glibc) resorted back to IANA (formerly Olson) db rules
    +    for those timezones.  Some libc (e.g. FreeBSD) uses a fixed rule.
    +    Other libc (e.g. musl) interpret that as no transition at all [1].
     
         In addition, distributions (notoriously Debian-derived, which uses IANA
         db for CST6CDT and the like) started to split "legacy" timezones
    @@ Commit message
         Signed-off-by: Đoàn Trần Công Danh <congdanhqx@gmail.com>
     
      ## t/t9604-cvsimport-timestamps.sh ##
    -@@ t/t9604-cvsimport-timestamps.sh: test_description='git cvsimport timestamps'
    +@@
    + test_description='git cvsimport timestamps'
    + . ./lib-cvs.sh
      
    ++test_lazy_prereq POSIX_TIMEZONE '
    ++	local tz=XST-1XDT,M3.5.0,M11.1.0
    ++	echo "1711846799 -> 2024-03-31 01:59:59 +0100" >expected &&
    ++	TZ="$tz" test-tool date show:iso-local 1711846799 >actual &&
    ++	test_cmp expected actual &&
    ++	echo "1711846800 -> 2024-03-31 03:00:00 +0200" >expected &&
    ++	TZ="$tz" test-tool date show:iso-local 1711846800 >actual &&
    ++	test_cmp expected actual &&
    ++	echo "1730591999 -> 2024-11-03 01:59:59 +0200" >expected &&
    ++	TZ="$tz" test-tool date show:iso-local 1730591999 >actual &&
    ++	test_cmp expected actual &&
    ++	echo "1730592000 -> 2024-11-03 01:00:00 +0100" >expected &&
    ++	TZ="$tz" test-tool date show:iso-local 1730592000 >actual &&
    ++	test_cmp expected actual
    ++'
    ++
      setup_cvs_test_repository t9604
      
     -test_expect_success PERL 'check timestamps are UTC (TZ=CST6CDT)' '
    -+test_expect_success PERL 'check timestamps are UTC (TZ=America/Chicago)' '
    ++test_expect_success PERL,POSIX_TIMEZONE 'check timestamps are UTC' '
      
     -	TZ=CST6CDT git cvsimport -p"-x" -C module-1 module &&
     +	TZ=CST6CDT,M4.1.0,M10.5.0 \
    @@ t/t9604-cvsimport-timestamps.sh: test_description='git cvsimport timestamps'
      	git cvsimport -p"-x" -C module-1 module &&
      	(
      		cd module-1 &&
    -@@ t/t9604-cvsimport-timestamps.sh: test_expect_success PERL 'check timestamps with author-specific timezones' '
    +@@ t/t9604-cvsimport-timestamps.sh: test_expect_success PERL 'check timestamps are UTC (TZ=CST6CDT)' '
    + 	test_cmp expect-1 actual-1
    + '
    + 
    +-test_expect_success PERL 'check timestamps with author-specific timezones' '
    ++test_expect_success PERL,POSIX_TIMEZONE 'check timestamps with author-specific timezones' '
      
      	cat >cvs-authors <<-EOF &&
      	user1=User One <user1@domain.org>

 t/t9604-cvsimport-timestamps.sh | 29 +++++++++++++++++++++++------
 1 file changed, 23 insertions(+), 6 deletions(-)