git-send-email: add support for TLS via Net::SMTP::SSL

We do this by handing over the Net::SMTP instance to Net::SMTP::SSL,
which avoids Net::SMTP::TLS and its weird error checking.  This trick
is due to Brian Evins.

Signed-off-by: Thomas Rast <trast@student.ethz.ch>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Documentation/git-send-email.txt

@@ -133,10 +133,13 @@ or on the command line. If a username has been specified (with
 specified (with --smtp-pass or a configuration variable), then the
 user is prompted for a password while the input is masked for privacy.
 
+--smtp-encryption::
+	Specify the encryption to use, either 'ssl' or 'tls'.  Any other
+	value reverts to plain SMTP.  Default is the value of
+	'sendemail.smtpencryption'.
+
 --smtp-ssl::
-	If set, connects to the SMTP server using SSL.
-	Default is the value of the 'sendemail.smtpssl' configuration value;
-	if that is unspecified, does not use SSL.
+	Legacy alias for '--smtp-encryption=ssl'.
 
 --subject::
 	Specify the initial subject of the email thread.
@@ -229,8 +232,13 @@ sendemail.smtpuser::
 sendemail.smtppass::
 	Default SMTP-AUTH password.
 
+sendemail.smtpencryption::
+	Default encryption method.  Use 'ssl' for SSL (and specify an
+	appropriate port), or 'tls' for TLS.  Takes precedence over
+	'smtpssl' if both are specified.
+
 sendemail.smtpssl::
-	Boolean value specifying the default to the '--smtp-ssl' parameter.
+	Legacy boolean that sets 'smtpencryption=ssl' if enabled.
 
 Author
 ------

git-send-email.perl

@@ -84,7 +84,10 @@ sub usage {
 
    --smtp-pass    The password for SMTP-AUTH.
 
-   --smtp-ssl     If set, connects to the SMTP server using SSL.
+   --smtp-encryption Specify 'tls' for STARTTLS encryption, or 'ssl' for SSL.
+                  Any other value disables the feature.
+
+   --smtp-ssl     Synonym for '--smtp-encryption=ssl'.  Deprecated.
 
    --suppress-cc  Suppress the specified category of auto-CC.  The category
 		  can be one of 'author' for the patch author, 'self' to
@@ -184,7 +187,7 @@ sub format_2822_time {
 
 # Variables with corresponding config settings
 my ($thread, $chain_reply_to, $suppress_from, $signed_off_cc, $cc_cmd);
-my ($smtp_server, $smtp_server_port, $smtp_authuser, $smtp_ssl);
+my ($smtp_server, $smtp_server_port, $smtp_authuser, $smtp_encryption);
 my ($identity, $aliasfiletype, @alias_files, @smtp_host_parts);
 my ($no_validate);
 my (@suppress_cc);
@@ -194,7 +197,6 @@ sub format_2822_time {
     "chainreplyto" => [\$chain_reply_to, 1],
     "suppressfrom" => [\$suppress_from, undef],
     "signedoffcc" => [\$signed_off_cc, undef],
-    "smtpssl" => [\$smtp_ssl, 0],
 );
 
 my %config_settings = (
@@ -249,7 +251,8 @@ sub signal_handler {
 		    "smtp-server-port=s" => \$smtp_server_port,
 		    "smtp-user=s" => \$smtp_authuser,
 		    "smtp-pass:s" => \$smtp_authpass,
-		    "smtp-ssl!" => \$smtp_ssl,
+		    "smtp-ssl" => sub { $smtp_encryption = 'ssl' },
+		    "smtp-encryption=s" => \$smtp_encryption,
 		    "identity=s" => \$identity,
 		    "compose" => \$compose,
 		    "quiet" => \$quiet,
@@ -289,6 +292,15 @@ sub read_config {
 			$$target = Git::config(@repo, "$prefix.$setting") unless (defined $$target);
 		}
 	}
+
+	if (!defined $smtp_encryption) {
+		my $enc = Git::config(@repo, "$prefix.smtpencryption");
+		if (defined $enc) {
+			$smtp_encryption = $enc;
+		} elsif (Git::config_bool(@repo, "$prefix.smtpssl")) {
+			$smtp_encryption = 'ssl';
+		}
+	}
 }
 
 # read configuration from [sendemail "$identity"], fall back on [sendemail]
@@ -738,7 +750,7 @@ sub send_message
 			die "The required SMTP server is not properly defined."
 		}
 
-		if ($smtp_ssl) {
+		if ($smtp_encryption eq 'ssl') {
 			$smtp_server_port ||= 465; # ssmtp
 			require Net::SMTP::SSL;
 			$smtp ||= Net::SMTP::SSL->new($smtp_server, Port => $smtp_server_port);
@@ -748,6 +760,17 @@ sub send_message
 			$smtp ||= Net::SMTP->new((defined $smtp_server_port)
 						 ? "$smtp_server:$smtp_server_port"
 						 : $smtp_server);
+			if ($smtp_encryption eq 'tls') {
+				require Net::SMTP::SSL;
+				$smtp->command('STARTTLS');
+				$smtp->response();
+				if ($smtp->code == 220) {
+					$smtp = Net::SMTP::SSL->start_SSL($smtp)
+						or die "STARTTLS failed! ".$smtp->message;
+				} else {
+					die "Server does not support STARTTLS! ".$smtp->message;
+				}
+			}
 		}
 
 		if (!$smtp) {