Add configure option to reduce visual clutter at boot time

Add configure option to reduce visual clutter at boot time

If this option is enabled, then do all of the following:

Don't display introductory message about line editing unless we're
actually offering a shell prompt.  (This is believed to be a workaround
for a different bug.  We'll go with this for now, but will drop this in
favour of a better fix upstream if somebody figures out what that is.)

Don't clear the screen just before booting if we never drew the menu in
the first place.

Remove verbose messages printed before reading configuration.  In some
ways this is awkward because it makes debugging harder, but it's a
requirement for a smooth-looking boot process; we may be able to do
better in future.  Upstream doesn't want this, though.

Disable the cursor as well, for similar reasons of tidiness.

Suppress kernel/initrd progress messages, except in recovery mode.

Suppress "GRUB loading" message unless Shift is held down.  Upstream
doesn't want this, as it makes debugging harder.  Ubuntu wants it to
provide a cleaner boot experience.

Author: Will Thompson <will@willthompson.co.uk>
Bug-Ubuntu: https://bugs.launchpad.net/bugs/386922
Bug-Ubuntu: https://bugs.launchpad.net/bugs/861048
Forwarded: (partial) http://lists.gnu.org/archive/html/grub-devel/2009-09/msg00056.html
Last-Update: 2021-09-24

Patch-Name: maybe-quiet.patch

Gbp-Pq: Name maybe-quiet.patch