send-email: add no-validate option

Since we are now sanity-checking the contents of patches and
refusing to send ones with long lines, this knob provides a
way for the user to override the new behavior (if, e.g., he
knows his SMTP path will handle it).

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

t/t9001-send-email.sh

@@ -98,4 +98,14 @@ test_expect_success 'no patch was sent' '
 	! test -e commandline
 '
 
+test_expect_success 'allow long lines with --no-validate' '
+	git send-email \
+		--from="Example <nobody@example.com>" \
+		--to=nobody@example.com \
+		--smtp-server="$(pwd)/fake.sendmail" \
+		--no-validate \
+		$patches longline.patch \
+		2>errors
+'
+
 test_done