Bug 1257243

Description of problem:
Even this might sound very strange, I would like to see an option for 
poweroff(1)/reboot(1) to describe why a shutdown/reboot takes place,
similar like the Microsoft Windows shutdown event tracker. When doing
server maintenance on production systems, I treat it as helpful to know
at a later point when scrolling through the logs why a reboot happened.

Upstream link: https://github.com/systemd/systemd/pull/1029/files

I could imagine something like this:

  reboot -m "Security update of kernel"

Or:

  poweroff -m "Replacement of defunct NIC"

So the goal would be to have this message finally logged in systemd's
journal (or /var/log/messages). I don't know if it makes sense to even
introduce predefined groups (which autofill -m), but my personal needs
would be satisfied with above. I indeed could call logger(1) or so, but
it would be nice to have it along with the command that I run anyway.

Version-Release number of selected component (if applicable):
systemd-208-20.el7_1.5.x86_64

Actual results:
No option for poweroff(1)/reboot(1) to describe why a shutdown/reboot
takes place.

Expected results:
Option for poweroff(1)/reboot(1) to describe why a shutdown/reboot takes
place.