Merge branch 'bc/send-email-auto-cte'

The content-transfer-encoding of the message "git send-email" sends
out by default was 8bit, which can cause trouble when there is an
overlong line to bust RFC 5322/2822 limit.  A new option 'auto' to
automatically switch to quoted-printable when there is such a line
in the payload has been introduced and is made the default.

* bc/send-email-auto-cte:
  docs: correct RFC specifying email line length
  send-email: automatically determine transfer-encoding
  send-email: accept long lines with suitable transfer encoding
  send-email: add an auto option for transfer encoding

Documentation/git-send-email.txt

@@ -137,15 +137,17 @@ Note that no attempts whatsoever are made to validate the encoding.
 	Specify encoding of compose message. Default is the value of the
 	'sendemail.composeencoding'; if that is unspecified, UTF-8 is assumed.
 
---transfer-encoding=(7bit|8bit|quoted-printable|base64)::
+--transfer-encoding=(7bit|8bit|quoted-printable|base64|auto)::
 	Specify the transfer encoding to be used to send the message over SMTP.
 	7bit will fail upon encountering a non-ASCII message.  quoted-printable
 	can be useful when the repository contains files that contain carriage
 	returns, but makes the raw patch email file (as saved from a MUA) much
 	harder to inspect manually.  base64 is even more fool proof, but also
-	even more opaque.  Default is the value of the `sendemail.transferEncoding`
-	configuration value; if that is unspecified, git will use 8bit and not
-	add a Content-Transfer-Encoding header.
+	even more opaque.  auto will use 8bit when possible, and quoted-printable
+	otherwise.
++
+Default is the value of the `sendemail.transferEncoding` configuration
+value; if that is unspecified, default to `auto`.
 
 --xmailer::
 --no-xmailer::
@@ -398,8 +400,11 @@ have been specified, in which case default to 'compose'.
 +
 --
 		*	Invoke the sendemail-validate hook if present (see linkgit:githooks[5]).
-		*	Warn of patches that contain lines longer than 998 characters; this
-			is due to SMTP limits as described by http://www.ietf.org/rfc/rfc2821.txt.
+		*	Warn of patches that contain lines longer than
+			998 characters unless a suitable transfer encoding
+			('auto', 'base64', or 'quoted-printable') is used;
+			this is due to SMTP limits as described by
+			http://www.ietf.org/rfc/rfc5322.txt.
 --
 +
 Default is the value of `sendemail.validate`; if this is not set,

git-send-email.perl

@@ -231,7 +231,7 @@ sub do_edit {
 my (@suppress_cc);
 my ($auto_8bit_encoding);
 my ($compose_encoding);
-my ($target_xfer_encoding);
+my $target_xfer_encoding = 'auto';
 
 my ($debug_net_smtp) = 0;		# Net::SMTP, see send_message()
 
@@ -645,7 +645,7 @@ sub is_format_patch_arg {
 if ($validate) {
 	foreach my $f (@files) {
 		unless (-p $f) {
-			my $error = validate_patch($f);
+			my $error = validate_patch($f, $target_xfer_encoding);
 			$error and die sprintf(__("fatal: %s: %s\nwarning: no patches were sent\n"),
 						  $f, $error);
 		}
@@ -1737,18 +1737,11 @@ sub process_file {
 			}
 		}
 	}
-	if (defined $target_xfer_encoding) {
-		$xfer_encoding = '8bit' if not defined $xfer_encoding;
-		$message = apply_transfer_encoding(
-			$message, $xfer_encoding, $target_xfer_encoding);
-		$xfer_encoding = $target_xfer_encoding;
-	}
-	if (defined $xfer_encoding) {
-		push @xh, "Content-Transfer-Encoding: $xfer_encoding";
-	}
-	if (defined $xfer_encoding or $has_content_type) {
-		unshift @xh, 'MIME-Version: 1.0' unless $has_mime_version;
-	}
+	$xfer_encoding = '8bit' if not defined $xfer_encoding;
+	($message, $xfer_encoding) = apply_transfer_encoding(
+		$message, $xfer_encoding, $target_xfer_encoding);
+	push @xh, "Content-Transfer-Encoding: $xfer_encoding";
+	unshift @xh, 'MIME-Version: 1.0' unless $has_mime_version;
 
 	$needs_confirm = (
 		$confirm eq "always" or
@@ -1852,13 +1845,16 @@ sub apply_transfer_encoding {
 	$message = MIME::Base64::decode($message)
 		if ($from eq 'base64');
 
+	$to = ($message =~ /.{999,}/) ? 'quoted-printable' : '8bit'
+		if $to eq 'auto';
+
 	die __("cannot send message as 7bit")
 		if ($to eq '7bit' and $message =~ /[^[:ascii:]]/);
-	return $message
+	return ($message, $to)
 		if ($to eq '7bit' or $to eq '8bit');
-	return MIME::QuotedPrint::encode($message, "\n", 0)
+	return (MIME::QuotedPrint::encode($message, "\n", 0), $to)
 		if ($to eq 'quoted-printable');
-	return MIME::Base64::encode($message, "\n")
+	return (MIME::Base64::encode($message, "\n"), $to)
 		if ($to eq 'base64');
 	die __("invalid transfer encoding");
 }
@@ -1877,7 +1873,7 @@ sub unique_email_list {
 }
 
 sub validate_patch {
-	my $fn = shift;
+	my ($fn, $xfer_encoding) = @_;
 
 	if ($repo) {
 		my $validate_hook = catfile(catdir($repo->repo_path(), 'hooks'),
@@ -1897,11 +1893,15 @@ sub validate_patch {
 		return $hook_error if $hook_error;
 	}
 
-	open(my $fh, '<', $fn)
-		or die sprintf(__("unable to open %s: %s\n"), $fn, $!);
-	while (my $line = <$fh>) {
-		if (length($line) > 998) {
-			return sprintf(__("%s: patch contains a line longer than 998 characters"), $.);
+	# Any long lines will be automatically fixed if we use a suitable transfer
+	# encoding.
+	unless ($xfer_encoding =~ /^(?:auto|quoted-printable|base64)$/) {
+		open(my $fh, '<', $fn)
+			or die sprintf(__("unable to open %s: %s\n"), $fn, $!);
+		while (my $line = <$fh>) {
+			if (length($line) > 998) {
+				return sprintf(__("%s: patch contains a line longer than 998 characters"), $.);
+			}
 		}
 	}
 	return;

t/t9001-send-email.sh

@@ -225,6 +225,8 @@ X-Mailer: X-MAILER-STRING
 In-Reply-To: <unique-message-id@example.com>
 References: <unique-message-id@example.com>
 Reply-To: Reply <reply@example.com>
+MIME-Version: 1.0
+Content-Transfer-Encoding: 8bit
 
 Result: OK
 EOF
@@ -415,6 +417,7 @@ test_expect_success $PREREQ 'reject long lines' '
 		--from="Example <nobody@example.com>" \
 		--to=nobody@example.com \
 		--smtp-server="$(pwd)/fake.sendmail" \
+		--transfer-encoding=8bit \
 		$patches longline.patch \
 		2>errors &&
 	grep longline.patch errors
@@ -456,6 +459,42 @@ test_expect_success $PREREQ 'allow long lines with --no-validate' '
 		2>errors
 '
 
+test_expect_success $PREREQ 'short lines with auto encoding are 8bit' '
+	clean_fake_sendmail &&
+	git send-email \
+		--from="A <author@example.com>" \
+		--to=nobody@example.com \
+		--smtp-server="$(pwd)/fake.sendmail" \
+		--transfer-encoding=auto \
+		$patches &&
+	grep "Content-Transfer-Encoding: 8bit" msgtxt1
+'
+
+test_expect_success $PREREQ 'long lines with auto encoding are quoted-printable' '
+	clean_fake_sendmail &&
+	git send-email \
+		--from="Example <nobody@example.com>" \
+		--to=nobody@example.com \
+		--smtp-server="$(pwd)/fake.sendmail" \
+		--transfer-encoding=auto \
+		--no-validate \
+		longline.patch &&
+	grep "Content-Transfer-Encoding: quoted-printable" msgtxt1
+'
+
+for enc in auto quoted-printable base64
+do
+	test_expect_success $PREREQ "--validate passes with encoding $enc" '
+		git send-email \
+			--from="Example <nobody@example.com>" \
+			--to=nobody@example.com \
+			--smtp-server="$(pwd)/fake.sendmail" \
+			--transfer-encoding=$enc \
+			--validate \
+			$patches longline.patch
+	'
+done
+
 test_expect_success $PREREQ 'Invalid In-Reply-To' '
 	clean_fake_sendmail &&
 	git send-email \
@@ -573,6 +612,8 @@ Subject: [PATCH 1/1] Second.
 Date: DATE-STRING
 Message-Id: MESSAGE-ID-STRING
 X-Mailer: X-MAILER-STRING
+MIME-Version: 1.0
+Content-Transfer-Encoding: 8bit
 
 Result: OK
 EOF
@@ -617,6 +658,8 @@ Subject: [PATCH 1/1] Second.
 Date: DATE-STRING
 Message-Id: MESSAGE-ID-STRING
 X-Mailer: X-MAILER-STRING
+MIME-Version: 1.0
+Content-Transfer-Encoding: 8bit
 
 Result: OK
 EOF
@@ -652,6 +695,8 @@ Subject: [PATCH 1/1] Second.
 Date: DATE-STRING
 Message-Id: MESSAGE-ID-STRING
 X-Mailer: X-MAILER-STRING
+MIME-Version: 1.0
+Content-Transfer-Encoding: 8bit
 
 Result: OK
 EOF
@@ -678,6 +723,8 @@ Subject: [PATCH 1/1] Second.
 Date: DATE-STRING
 Message-Id: MESSAGE-ID-STRING
 X-Mailer: X-MAILER-STRING
+MIME-Version: 1.0
+Content-Transfer-Encoding: 8bit
 
 Result: OK
 EOF
@@ -712,6 +759,8 @@ Subject: [PATCH 1/1] Second.
 Date: DATE-STRING
 Message-Id: MESSAGE-ID-STRING
 X-Mailer: X-MAILER-STRING
+MIME-Version: 1.0
+Content-Transfer-Encoding: 8bit
 
 Result: OK
 EOF
@@ -743,6 +792,8 @@ Subject: [PATCH 1/1] Second.
 Date: DATE-STRING
 Message-Id: MESSAGE-ID-STRING
 X-Mailer: X-MAILER-STRING
+MIME-Version: 1.0
+Content-Transfer-Encoding: 8bit
 
 Result: OK
 EOF
@@ -774,6 +825,8 @@ Subject: [PATCH 1/1] Second.
 Date: DATE-STRING
 Message-Id: MESSAGE-ID-STRING
 X-Mailer: X-MAILER-STRING
+MIME-Version: 1.0
+Content-Transfer-Encoding: 8bit
 
 Result: OK
 EOF
@@ -809,6 +862,8 @@ Subject: [PATCH 1/1] Second.
 Date: DATE-STRING
 Message-Id: MESSAGE-ID-STRING
 X-Mailer: X-MAILER-STRING
+MIME-Version: 1.0
+Content-Transfer-Encoding: 8bit
 
 Result: OK
 EOF
@@ -837,6 +892,8 @@ Subject: [PATCH 1/1] Second.
 Date: DATE-STRING
 Message-Id: MESSAGE-ID-STRING
 X-Mailer: X-MAILER-STRING
+MIME-Version: 1.0
+Content-Transfer-Encoding: 8bit
 
 Result: OK
 EOF