unit: ship a mail-transfer-agent.target unit by default

Makefile.am

@@ -87,6 +87,7 @@ dist_systemunit_DATA = \
 	units/local-fs.target \
 	units/network.target \
 	units/nss-lookup.target \
+	units/mail-transfer-agent.target \
 	units/poweroff.target \
 	units/reboot.target \
 	units/remote-fs.target \

man/systemd.special.xml.in

@@ -57,6 +57,7 @@
                 <filename>halt.target</filename>,
                 <filename>kbrequest.target</filename>,
                 <filename>local-fs.target</filename>,
+                <filename>mail-transfer-agent.target</filename>,
                 <filename>multi-user.target</filename>,
                 <filename>network.target</filename>,
                 <filename>nss-lookup.target</filename>,
@@ -248,6 +249,29 @@
                                         facility.</para>
                                 </listitem>
                         </varlistentry>
+                        <varlistentry>
+                                <term><filename>mail-transfer-agent.target</filename></term>
+                                <listitem>
+                                        <para>The mail transfer agent
+                                        (MTA) service. Usually this
+                                        should pull in all units
+                                        necessary for
+                                        sending/receiving mails on the
+                                        local host.</para>
+
+                                        <para>systemd automatically
+                                        adds dependencies of type
+                                        After for this target unit to
+                                        all SysV init script service
+                                        units with an LSB header
+                                        referring to the
+                                        <literal>$mail-transfer-argent</literal>
+                                        or
+                                        <literal>$mail-transport-agent</literal>
+                                        facilities, for compatibility
+                                        with Debian.</para>
+                                </listitem>
+                        </varlistentry>
                         <varlistentry>
                                 <term><filename>multi-user.target</filename></term>
                                 <listitem>

units/mail-transfer-agent.target

@@ -0,0 +1,11 @@
+#  This file is part of systemd.
+#
+#  systemd is free software; you can redistribute it and/or modify it
+#  under the terms of the GNU General Public License as published by
+#  the Free Software Foundation; either version 2 of the License, or
+#  (at your option) any later version.
+
+# See systemd.special(7) for details
+
+[Unit]
+Description=Mail Transfer Agent