perl: call timegm and timelocal with 4-digit year

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>

1 files changed, 1 insertions, 1 deletions

diff --git a/contrib/examples/git-svnimport.perl b/contrib/examples/git-svnimport.perl
index c414f0d..75a43e2 100755
--- a/contrib/examples/git-svnimport.perl
+++ b/contrib/examples/git-svnimport.perl
@@ -238,7 +238,7 @@ sub pdate($) {
 	my($d) = @_;
 	$d =~ m#(\d\d\d\d)-(\d\d)-(\d\d)T(\d\d):(\d\d):(\d\d)#
 		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);
 }