Add 'notify:pid' style readiness notifaction and 'readiness none'

This change expands the readiness notification system in Finit with the
native 'pid' style, which will remain the default readiness in Finit 4.x

For systems that want to transition to Finit 5.x early, a global option
to set 'readiness none' in /etc/finit.conf, has been added.  This change
the service default notification mode to 'notify:none', which can also
be set by Finit 4.x ('readiness pid') for select services.

Fixes #386.

Signed-off-by: Joachim Wiberg <troglobit@gmail.com>

system/10-hotplug.conf.in

@@ -18,8 +18,8 @@
 # change the contents any way you like, it can even be empty.
 
 # Check for systemd-udevd and eudev, if we find both, we opt for the latter.
-service nowarn [S12345789] cgroup.system name:udevd pid:udevd log /lib/systemd/systemd-udevd -- Device event daemon (udev)
-service nowarn [S12345789] cgroup.system name:udevd pid:udevd log udevd -D -- Device event daemon (udev)
+service nowarn [S12345789] cgroup.system name:udevd notify:none pid:udevd log /lib/systemd/systemd-udevd -- Device event daemon (udev)
+service nowarn [S12345789] cgroup.system name:udevd notify:none pid:udevd log udevd -D -- Device event daemon (udev)
 
 # Wait for udevd to start, then trigger coldplug events and module loading.
 # The last 'settle' call waits for it to finalize processing all uevents.
@@ -34,7 +34,7 @@ run nowarn if:udevd cgroup.init :5 [S] <pid/udevd> log udevadm settle -t 30
 # <run/coldplug/success> (same as for plain mdev below) can be relied on as a
 # barrier for services that, e.g., need to probe for switchcore ports or PHYs
 # that require firmware loading before they show up.
-service nowarn conflict:udevd,mdev cgroup.init if:!udevd \
+service nowarn conflict:udevd,mdev cgroup.init notify:none if:!udevd \
 	[S12345789] notify:s6 mdevd -O 4 -D %n -- Device event daemon (mdevd)
 run     nowarn conflict:udevd,mdev cgroup.init name:coldplug <service/mdevd/ready> \
 	[S] mdevd-coldplug -- Cold plugging system
@@ -42,7 +42,7 @@ run     nowarn conflict:udevd,mdev cgroup.init name:coldplug <service/mdevd/read
 # If neither udevd or mdevd are available, fall back to mdev.  The new daemon
 # mode calls `mdev -s` internally but does not create a PID file when that is
 # done, so synchronization with coldplug is fragile.
-service nowarn conflict:udevd,mdevd cgroup.init if:!udevd,!mdevd \
+service nowarn conflict:udevd,mdevd cgroup.init notify:none if:!udevd,!mdevd \
 	[S12345789] mdev -df -S -- Device event daemon (mdev)
 
 # Trigger a replay of all uevents from boot, before userspace was up and the

system/90-testserv.conf

@@ -1,4 +1,4 @@
 # Test service, only used for `make check`, not for public use
 service [S123456789] name:testserv pid:!/run/testserv.pid \
-	<boot/testserv> cgroup.system \
+	<boot/testserv> cgroup.system notify:none \
 	/sbin/serv -n -p -i testserv -- Test serv daemon