send-email: allow sendmail binary to be used instead of SMTP

This should make local mailing possible for machines without
a connection to an SMTP server.

It'll default to using /usr/sbin/sendmail or /usr/lib/sendmail
if no SMTP server is specified (the default).  If it can't find
either of those paths, it'll fall back to connecting to an SMTP
server on localhost.

Signed-off-by: Eric Wong <normalperson@yhbt.net>
Signed-off-by: Junio C Hamano <junkio@cox.net>

git-send-email.perl

@@ -40,7 +40,8 @@
 my (@to,@cc,@initial_cc,$initial_reply_to,$initial_subject,@files,$from,$compose,$time);
 
 # Behavior modification variables
-my ($chain_reply_to, $smtp_server, $quiet, $suppress_from, $no_signed_off_cc) = (1, "localhost", 0, 0, 0);
+my ($chain_reply_to, $quiet, $suppress_from, $no_signed_off_cc) = (1, 0, 0, 0);
+my $smtp_server;
 
 # Example reply to:
 #$initial_reply_to = ''; #<20050203173208.GA23964@foobar.com>';
@@ -179,8 +180,14 @@ sub expand_aliases {
 	$initial_reply_to =~ s/(^\s+|\s+$)//g;
 }
 
-if (!defined $smtp_server) {
-	$smtp_server = "localhost";
+if (!$smtp_server) {
+	foreach (qw( /usr/sbin/sendmail /usr/lib/sendmail )) {
+		if (-x $_) {
+			$smtp_server = $_;
+			last;
+		}
+	}
+	$smtp_server ||= 'localhost'; # could be 127.0.0.1, too... *shrug*
 }
 
 if ($compose) {
@@ -358,26 +365,39 @@ sub send_message
 ";
 	$header .= "In-Reply-To: $reply_to\n" if $reply_to;
 
-	$smtp ||= Net::SMTP->new( $smtp_server );
-	$smtp->mail( $from ) or die $smtp->message;
-	$smtp->to( @recipients ) or die $smtp->message;
-	$smtp->data or die $smtp->message;
-	$smtp->datasend("$header\n$message") or die $smtp->message;
-	$smtp->dataend() or die $smtp->message;
-	$smtp->ok or die "Failed to send $subject\n".$smtp->message;
-
+	if ($smtp_server =~ m#^/#) {
+		my $pid = open my $sm, '|-';
+		defined $pid or die $!;
+		if (!$pid) {
+			exec($smtp_server,'-i',@recipients) or die $!;
+		}
+		print $sm "$header\n$message";
+		close $sm or die $?;
+	} else {
+		$smtp ||= Net::SMTP->new( $smtp_server );
+		$smtp->mail( $from ) or die $smtp->message;
+		$smtp->to( @recipients ) or die $smtp->message;
+		$smtp->data or die $smtp->message;
+		$smtp->datasend("$header\n$message") or die $smtp->message;
+		$smtp->dataend() or die $smtp->message;
+		$smtp->ok or die "Failed to send $subject\n".$smtp->message;
+	}
 	if ($quiet) {
 		printf "Sent %s\n", $subject;
 	} else {
-		print "OK. Log says:
-Date: $date
-Server: $smtp_server Port: 25
-From: $from
-Subject: $subject
-Cc: $cc
-To: $to
-
-Result: ", $smtp->code, ' ', ($smtp->message =~ /\n([^\n]+\n)$/s), "\n";
+		print "OK. Log says:\nDate: $date\n";
+		if ($smtp) {
+			print "Server: $smtp_server\n";
+		} else {
+			print "Sendmail: $smtp_server\n";
+		}
+		print "From: $from\nSubject: $subject\nCc: $cc\nTo: $to\n\n";
+		if ($smtp) {
+			print "Result: ", $smtp->code, ' ',
+				($smtp->message =~ /\n([^\n]+\n)$/s), "\n";
+		} else {
+			print "Result: OK\n";
+		}
 	}
 }