[__lxc_container] add --restart-if-changed parameter to apply changes

This parameter restarts the container if configuration changes and it is
already running and should keept running. It handles the freeze state,
because it would be expected to apply changes in this state, too.

cdist/conf/type/__lxc_container/gencode-remote

@@ -234,8 +234,55 @@ DONE
 rm -rf "$container_config"
 mv "\$tmpconfig" "$container_config"
 DONE
-	# write message
 	echo "config" >> "$__messages_out"
+
+
+	# restart container only if it is running
+	#  do not echo messages start/stop or melt/start/stop/freeze; only restart to avoid junk
+	case "$state_is" in
+		running|frozen)
+			# only do it if the container will run again
+			case "$state_should" in
+				present|running|frozen)
+					# su stuff
+					cat <<USER
+su "$user" - <<SU
+USER
+
+					# unfreeze if required
+					if [ "$state_is" = "frozen" ]; then
+						cat <<LXC
+lxc-unfreeze $LXC_PARAM -n "$name"
+LXC
+					fi
+
+					# stop and start
+					cat <<LXC
+lxc-stop $LXC_PARAM -n "$name"
+lxc-start $LXC_PARAM -n "$name"
+LXC
+
+					# freeze it again if it was there before, but be clever
+					# if $state_is = running but should be frozen, later code will do that
+					if [ "$state_is" = "frozen" ]; then
+						if [ "$state_should" = "frozen" ] || [ "$state_should" = "present" ]; then
+							cat <<LXC
+lxc-freeze $LXC_PARAM -n "$name"
+LXC
+						else
+							# correct current state
+							state_is="running"
+							echo "melt" >> "$__messages_out"
+						fi
+					fi
+
+					# ending
+					echo "restart" >> "$__messages_out"
+					echo "SU"
+				;;
+			esac
+			;;
+	esac
 fi
 
 

cdist/conf/type/__lxc_container/man.rst

@@ -70,7 +70,11 @@ config-absent
 
 BOOLEAN PARAMETERS
 ------------------
-None.
+
+restart-if-changed
+    Restarts the container if configuration changes. It stop and start the container that new configuration
+    can be applied. If it whould be restarted with ``lxc-stop -n $name --reboot``, configuration changes
+    would be ignored.
 
 CREATE PARAMETERS
 -----------------

cdist/conf/type/__lxc_container/parameter/boolean

@@ -1 +1,2 @@
 no-default-config
+restart-if-changed