Bug#918966: new(?) backlight brightness script

[Dmitry Bogatov]

[2019-01-17 21:13] Thorsten Glaser <t.glaser at tarent.de>
> On Sat, 12 Jan 2019, Dmitry Bogatov wrote:
> 
> > Sure. Your contribution would be welcome.
> 
> I pushed it to a branch “tg-brightness” in the sysvinit
> packaging on Salsa.

Next time, wip/ namespace is preferred. It makes it clear,
that force-push are to be expected.

> I decided to rework the init script, so it can even work
> on multiple backlight brightness knobs, and added the
> Intel one from my Thinkpad, keeping the ACPI one compatible.

Thank you. But I have some considerations:

 * If no knob is found, all actions are silent. I believe some
   log_success_msg "brighntess not found" would be nice.

 * You merge 'start' and 'restart' action. Restart, by
   definition, is stop->start.

 * You did not declare MSG `local'. Why?

 * `local' is not mandated by POSIX. Does all posix-like
    shells in Debian support it?

 * In most cases, initscripts use '[ "${VERBOSE}" != no ]' snippet. Could you
   please convert to this style?

 * I believe, that "x$foo" is unnecessary. "$foo" expands to "" if $foo
   is empty.