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perl: call timegm and timelocal with 4-digit year

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Amazingly, timegm(gmtime(0)) is only 0 before 2020 because perl's
timegm deviates from GNU timegm(3) in how it handles years.

man Time::Local says

 Whenever possible, use an absolute four digit year instead.

with a detailed explanation about ambiguity of 2-digit years above that.

Even though this ambiguity is error-prone with >50% of users getting it
wrong, it has been like this for 20+ years, so we just use 4-digit years
everywhere to be on the safe side.

We add some extra logic to cvsimport because it allows 2-digit year
input and interpreting an 18 as 1918 can be avoided easily and safely.

Signed-off-by: Bernhard M. Wiedemann <bwiedemann@suse.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
This commit is contained in:
Bernhard M. Wiedemann 2018-02-23 18:20:45 +01:00 committed by Junio C Hamano
parent ffa9524972
commit a40e06ee33
4 changed files with 8 additions and 4 deletions
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2
contrib/examples/git-svnimport.perl
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@ -238,7 +238,7 @@ sub pdate($) {
my($d) = @_; my($d) = @_;
$d =~ m#(\d\d\d\d)-(\d\d)-(\d\d)T(\d\d):(\d\d):(\d\d)# $d =~ m#(\d\d\d\d)-(\d\d)-(\d\d)T(\d\d):(\d\d):(\d\d)#
or die "Unparseable date: $d\n"; or die "Unparseable date: $d\n";
my $y=$1; $y-=1900 if $y>1900; my $y=$1; $y+=1900 if $y<1000;
return timegm($6||0,$5,$4,$3,$2-1,$y); return timegm($6||0,$5,$4,$3,$2-1,$y);
} }

4
git-cvsimport.perl
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@ -601,7 +601,9 @@ sub pdate($) {
my ($d) = @_; my ($d) = @_;
m#(\d{2,4})/(\d\d)/(\d\d)\s(\d\d):(\d\d)(?::(\d\d))?# m#(\d{2,4})/(\d\d)/(\d\d)\s(\d\d):(\d\d)(?::(\d\d))?#
or die "Unparseable date: $d\n"; or die "Unparseable date: $d\n";
my $y=$1; $y-=1900 if $y>1900; my $y=$1;
$y+=100 if $y<70;
$y+=1900 if $y<1000;
return timegm($6||0,$5,$4,$3,$2-1,$y); return timegm($6||0,$5,$4,$3,$2-1,$y);
} }

4
perl/Git.pm
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@ -534,7 +534,9 @@ If TIME is not supplied, the current local time is used.
sub get_tz_offset { sub get_tz_offset {
# some systems don't handle or mishandle %z, so be creative. # some systems don't handle or mishandle %z, so be creative.
my $t = shift || time; my $t = shift || time;
my $gm = timegm(localtime($t)); my @t = localtime($t);
$t[5] += 1900;
my $gm = timegm(@t);
my $sign = qw( + + - )[ $gm <=> $t ]; my $sign = qw( + + - )[ $gm <=> $t ];
return sprintf("%s%02d%02d", $sign, (gmtime(abs($t - $gm)))[2,1]); return sprintf("%s%02d%02d", $sign, (gmtime(abs($t - $gm)))[2,1]);
} }

2
perl/Git/SVN.pm
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@ -1405,7 +1405,7 @@ sub parse_svn_date {
$ENV{TZ} = 'UTC'; $ENV{TZ} = 'UTC';
my $epoch_in_UTC = my $epoch_in_UTC =
Time::Local::timelocal($S, $M, $H, $d, $m - 1, $Y - 1900); Time::Local::timelocal($S, $M, $H, $d, $m - 1, $Y);
# Determine our local timezone (including DST) at the # Determine our local timezone (including DST) at the
# time of $epoch_in_UTC. $Git::SVN::Log::TZ stored the # time of $epoch_in_UTC. $Git::SVN::Log::TZ stored the