[__motd] Improve documentation and support for FreeBSD

This makes it easier to use the type just by reading the man page and also
treats FreeBSD's MOTD better.

cdist/conf/type/__motd/gencode-remote

@@ -29,7 +29,18 @@ case "$os" in
         echo "uname -snrvm > /var/run/motd"
         echo "cat /etc/motd.tail >> /var/run/motd"
     ;;
+    freebsd)
+        # FreeBSD only updates /etc/motd on boot,
+	# as seen in /etc/rc.d/motd
+	echo "uname -sri > /etc/motd"
+	echo "cat /etc/motd.template >> /etc/motd"
+	# FreeBSD 13 starts treating motd slightly different from previous
+	# versions this ensures hosts have the expected config.
+	echo "rm /etc/motd.template || true"
+	echo "service motd start"
+    ;;
     *)
+        # Other OS tend to treat /etc/motd statically
         exit 0
     ;;
 esac

cdist/conf/type/__motd/man.rst

@@ -10,6 +10,13 @@ DESCRIPTION
 -----------
 This cdist type allows you to easily setup /etc/motd.
 
+.. note::
+      In some OS, motd is a bit special, check `motd(5)`.
+      Currently Debian, Devuan, Ubuntu and FreeBSD are taken into account.
+      If your OS of choice does something besides /etc/motd, check the source
+      and contribute support for it.
+      Otherwise it will likely just work.
+
 
 REQUIRED PARAMETERS
 -------------------
@@ -20,6 +27,7 @@ OPTIONAL PARAMETERS
 -------------------
 source
    If supplied, copy this file from the host running cdist to the target.
+   If source is '-' (dash), take what was written to stdin as the file content.
    If not supplied, a default message will be placed onto the target.
 
 
@@ -34,6 +42,15 @@ EXAMPLES
     # Supply source file from a different type
     __motd --source "$__type/files/my-motd"
 
+    # Supply source from stdin
+    __motd --source "-" <<EOF
+    Take this kiss upon the brow!
+    And, in parting from you now,
+    Thus much let me avow-
+    You are not wrong, who deem
+    That my days have been a dream
+    EOF
+
 
 AUTHORS
 -------
@@ -42,7 +59,7 @@ Nico Schottelius <nico-cdist--@--schottelius.org>
 
 COPYING
 -------
-Copyright \(C) 2011 Nico Schottelius. You can redistribute it
+Copyright \(C) 2020 Nico Schottelius. 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 3 of the
 License, or (at your option) any later version.

cdist/conf/type/__motd/manifest

@@ -34,9 +34,17 @@ os=$(cat "$__global/explorer/os")
 
 case "$os" in
    debian|ubuntu|devuan)
+      # Debian-based systems use /etc/motd.tail as a template
       destination=/etc/motd.tail
    ;;
+   freebsd)
+      # FreeBSD uses motd.template to prepend system information on boot
+      # (this actually only applies starting with version 13,
+      #  but we fix that for whatever version in gencode-remote)
+      destination=/etc/motd.template
+   ;;
    *)
+      # Most UNIX systems, including other Linux and OpenBSD just use /etc/motd
       destination=/etc/motd
    ;;
 esac