git-svn: fix parsing of timestamp obtained from svn

Ward Wouts reports that git-svn barfed like this:

    Unable to parse date: 2004-03-09T09:44:33.Z at /usr/bin/git-svn line 3995

The parse_svn_date sub expects there always are one or more digits after
the decimal point to record fractional seconds, but this example does not
and results in a failure like this.

The fix is based on the original fix by the reporter, further cleaned up.
Signed-off-by: NJunio C Hamano <gitster@pobox.com>
Acked-by: NEric Wong <normalperson@yhbt.net>

git-svn.perl

@@ -2526,7 +2526,7 @@ sub get_untracked {
 sub parse_svn_date {
 	my $date = shift || return '+0000 1970-01-01 00:00:00';
 	my ($Y,$m,$d,$H,$M,$S) = ($date =~ /^(\d{4})\-(\d\d)\-(\d\d)T
-	                                    (\d\d)\:(\d\d)\:(\d\d).\d+Z$/x) or
+	                                    (\d\d)\:(\d\d)\:(\d\d)\.\d*Z$/x) or
 	                                 croak "Unable to parse date: $date\n";
 	my $parsed_date;    # Set next.