maillog: Support logging to stdout and stderr

This patch adds support for writing maillog to stdout and stderr, which
can be desirable in certain environments.

Thanks to Denys Vitali <denys@denv.it> who sent an alternative patch for
this functionality.

test/t-17-maillog/.gitignore

@@ -0,0 +1 @@
+config/chasquid.conf

test/t-17-maillog/config/chasquid.conf.in

@@ -0,0 +1,10 @@
+smtp_address: ":1025"
+submission_address: ":1587"
+submission_over_tls_address: ":1465"
+monitoring_address: ":1099"
+
+mail_delivery_agent_bin: "test-mda"
+mail_delivery_agent_args: "%to%"
+
+data_dir: "../.data"
+mail_log_path: "$MAIL_LOG_PATH"

test/t-17-maillog/content

@@ -0,0 +1,4 @@
+Subject: Prueba desde el test
+
+Crece desde el test el futuro
+Crece desde el test

test/t-17-maillog/hosts

@@ -0,0 +1 @@
+testserver localhost

test/t-17-maillog/msmtprc

@@ -0,0 +1,28 @@
+account default
+
+host testserver
+port 1587
+
+tls on
+tls_trust_file config/certs/testserver/fullchain.pem
+
+from user@testserver
+
+auth on
+user user@testserver
+password secretpassword
+
+account smtpport : default
+port 1025
+
+account subm_tls : default
+port 1465
+tls_starttls off
+
+account baduser : default
+user unknownuser@testserver
+password secretpassword
+
+account badpasswd : default
+user user@testserver
+password badsecretpassword

test/t-17-maillog/run.sh

@@ -0,0 +1,48 @@
+#!/bin/bash
+
+set -e
+. $(dirname ${0})/../util/lib.sh
+
+init
+
+mkdir -p .logs
+
+generate_certs_for testserver
+add_user user@testserver secretpassword
+add_user someone@testserver secretpassword
+
+function send_one() {
+	rm -f .logs/mail_log .logs/stdout .logs/stderr
+	envsubst < config/chasquid.conf.in > config/chasquid.conf
+
+	chasquid -v=2 --logfile=.logs/chasquid.log --config_dir=config \
+		> .logs/stdout 2> .logs/stderr &
+	wait_until_ready 1025
+
+	run_msmtp someone@testserver < content
+	wait_for_file .mail/someone@testserver
+	mail_diff content .mail/someone@testserver
+
+	pkill -s 0 chasquid
+	sleep 0.2
+}
+
+export MAIL_LOG_PATH="../.logs/mail_log"
+send_one
+if ! grep -q "from=user@testserver all done" .logs/mail_log; then
+	fail "entries not found in .logs/mail_log"
+fi
+
+export MAIL_LOG_PATH="<stdout>"
+send_one
+if ! grep -q "from=user@testserver all done" .logs/stdout; then
+	fail "entries not found in .logs/stdout"
+fi
+
+export MAIL_LOG_PATH="<stderr>"
+send_one
+if ! grep -q "from=user@testserver all done" .logs/stderr; then
+	fail "entries not found in .logs/stderr"
+fi
+
+success