Add systemd unit files

Largely inspired by https://lwn.net/Articles/584175/
"They must be suitable for every distribution to use."

Packagers must define:
- ExecStart=/path/to/bip_env.sh
- Environment=BIP_DEFAULT_CONFIG='/path/to/default/bip'
using a unit file drop-in bip-config.service.d/<distrib>.conf

Makefile.am

@@ -24,4 +24,5 @@ dist_examples_DATA = samples/bip.conf samples/bip.vim
 EXTRA_DIST = \
 	BUGS \
 	scripts/bip-release \
-	scripts/bipgenconfig
+	scripts/bipgenconfig \
+	systemd

systemd/README

@@ -0,0 +1,20 @@
+Notes about systemd unit files for bip.
+
+Distro specific commandline configuration is provided by installing a script
+named. A default script named bip_env.sh is provided.
+
+This should write /run/sysconfig/bip based on configuration
+information such as in /etc/sysconfig/bip or /etc/defaults/bip. It is run once
+by bip-config.service.
+
+Distro specific path for bip_env.sh script must be set using a
+bip-config.service.d/distrib.conf unit file drop-in:
+[Service]
+ExecStart=/path/to/bip_env.sh
+
+bip_env.sh try some default paths for the default configuration file: either
+/etc/default/bip or /etc/sysconfig/bip.
+Optionaly, the default configuration file path can be set too:
+[Service]
+ExecStart=/path/to/bip_env.sh
+Environment=BIP_DEFAULT_CONFIG='/path/to/default/bip'

systemd/bip-config.service

@@ -0,0 +1,12 @@
+[Unit]
+Description=Preprocess Bip configuration
+After=local-fs.target
+DefaultDependencies=no
+
+[Service]
+Type=oneshot
+RemainAfterExit=no
+# Packagers must define:
+# - ExecStart=/path/to/bip_env.sh
+# - Environment='BIP_DEFAULT_CONFIG=/path/to/default/bip'
+# using a unit file drop-in bip-config.service.d/<distrib>.conf

systemd/bip.service

@@ -0,0 +1,23 @@
+[Unit]
+Description=Bip IRC Proxy
+Requires=network.target
+
+Wants=bip-config.service
+After=bip-config.service
+
+[Service]
+EnvironmentFile=/run/sysconfig/bip
+
+Type=forking
+User=bip
+Group=bip
+ExecStartPre=/bin/sh -c '[ $ENABLED != 0 ]'
+ExecStart=/usr/bin/bip $DAEMON_ARGS
+ExecReload=/bin/kill -HUP $MAINPID
+RuntimeDirectory=bip
+RuntimeDirectoryMode=0750
+KillMode=process
+Restart=on-abnormal
+
+[Install]
+WantedBy=multi-user.target

systemd/bip_env.sh

@@ -0,0 +1,40 @@
+#!/bin/sh
+# Create /run/sysconfig/bip from default configuration file, for
+# bip-config.service
+
+# BIP_DEFAULT_CONFIG environment variable can be defined by packagers in a
+# drop-in override of bip-config.service unit
+if [ -n "${BIP_DEFAULT_CONFIG}" ]; then
+    # try some default paths
+    if [ -r /etc/default/bip ]; then
+        BIP_DEFAULT_CONFIG=/etc/default/bip
+        . "${BIP_DEFAULT_CONFIG}"
+    elif [ -r /etc/sysconfig/bip ]; then
+        BIP_DEFAULT_CONFIG=/etc/sysconfig/bip
+        . "${BIP_DEFAULT_CONFIG}"
+    fi
+else
+    . "${BIP_DEFAULT_CONFIG}"
+fi
+
+ENABLED=${ENABLED:-1}
+
+mkdir -p /run/sysconfig
+{
+echo ENABLED=${ENABLED}
+DAEMON_HOME=${DAEMON_HOME:-/var/lib/bip}
+DAEMON_CONFIG=${DAEMON_CONFIG:-/etc/bip/bip.conf}
+echo "DAEMON_ARGS=${DAEMON_ARGS:--f '${DAEMON_CONFIG}' -s '${DAEMON_HOME}'}"
+} > /run/sysconfig/bip
+
+if [ ${ENABLED} = 0 ]; then
+    echo "INFO: BIP is explicitely disabled (ENABLED == 0) in" \
+         "'${BIP_DEFAULT_CONFIG}'."
+else
+    if [ -n "${DAEMON_USER}" -o -n "${DAEMON_GROUP}" ]; then
+        echo "ERROR: Using systemd, DAEMON_USER and DAEMON_GROUP could not" \
+             "be defined using the default configuration file. A drop-in" \
+             "override of bip-config.service unit need to be created instead."
+        exit 1
+    fi
+fi