send-email: format 2822 datestring ourselves.

It is not worth trying to force C locale (and failing) just to
format the 2822 datestring.

This code was borrowed from /usr/bin/822-date (Ian Jackson and
Klee Dienes, both in public domain), per suggestion by Eric Wong.
Signed-off-by: NJunio C Hamano <junkio@cox.net>
Acked-by: NJakub Narebski <jnareb@gmail.com>

git-send-email.perl

@@ -34,8 +34,43 @@ sub readline {
 package main;
 
 # most mail servers generate the Date: header, but not all...
-$ENV{LC_ALL} = 'C';
-use POSIX qw/strftime/;
+sub format_2822_time {
+	my ($time) = @_;
+	my @localtm = localtime($time);
+	my @gmttm = gmtime($time);
+	my $localmin = $localtm[1] + $localtm[2] * 60;
+	my $gmtmin = $gmttm[1] + $gmttm[2] * 60;
+	if ($localtm[0] != $gmttm[0]) {
+		die "local zone differs from GMT by a non-minute interval\n";
+	}
+	if ((($gmttm[6] + 1) % 7) == $localtm[6]) {
+		$localmin += 1440;
+	} elsif ((($gmttm[6] - 1) % 7) == $localtm[6]) {
+		$localmin -= 1440;
+	} elsif ($gmttm[6] != $localtm[6]) {
+		die "local time offset greater than or equal to 24 hours\n";
+	}
+	my $offset = $localmin - $gmtmin;
+	my $offhour = $offset / 60;
+	my $offmin = abs($offset % 60);
+	if (abs($offhour) >= 24) {
+		die ("local time offset greater than or equal to 24 hours\n");
+	}
+
+	return sprintf("%s, %2d %s %d %02d:%02d:%02d %s%02d%02d",
+		       qw(Sun Mon Tue Wed Thu Fri Sat)[$localtm[6]],
+		       $localtm[3],
+		       qw(Jan Feb Mar Apr May Jun
+			  Jul Aug Sep Oct Nov Dec)[$localtm[4]],
+		       $localtm[5]+1900,
+		       $localtm[2],
+		       $localtm[1],
+		       $localtm[0],
+		       ($offset >= 0) ? '+' : '-',
+		       abs($offhour),
+		       $offmin,
+		       );
+}
 
 my $have_email_valid = eval { require Email::Valid; 1 };
 my $smtp;
@@ -387,7 +422,7 @@ sub send_message
 	my @recipients = unique_email_list(@to);
 	my $to = join (",\n\t", @recipients);
 	@recipients = unique_email_list(@recipients,@cc,@bcclist);
-	my $date = strftime('%a, %d %b %Y %H:%M:%S %z', localtime($time++));
+	my $date = format_2822_time($time++);
 	my $gitversion = '@@GIT_VERSION@@';
 	if ($gitversion =~ m/..GIT_VERSION../) {
 	    $gitversion = `git --version`;