Downgrade "aufs-tools" and "cgroupfs-mount" to "Suggests"

[tianon]

Quoting from https://www.debian.org/doc/debian-policy/ch-relationships.html#binary-dependencies-depends-recommends-suggests-enhances-pre-depends (as a refresher/context):

Recommends

This declares a strong, but not absolute, dependency.

The Recommends field should list packages that would be found together with this one in all but unusual installations.

Suggests

This is used to declare that one package may be more useful with one or more others. Using this field tells the packaging system and the user that the listed packages are related to this one and can perhaps enhance its usefulness, but that installing this one without them is perfectly reasonable.

My justification for this change, given that context, is that aufs hasn't been the default graph driver for quite some time now, and I'd wager the majority of new installations these days already have cgroups via systemd or some other similar package, so it's going to be less common for users to need something like cgroupfs-mount (and pulling it in on systemd-using systems is a noop that just generates noise).

(Another way to consider this is that in a properly configured APT installation, Recommends get installed by default but Suggests do not. 😄)

There has been some discussion around the former in https://bugs.debian.org/948087 recently that prompted me to finally pull the trigger on opening this, but it's something I've been thinking about for quite some time now.

[AkihiroSuda]

Can we just drop them?

[thaJeztah]

Ah, yes, been meaning to look at this, thanks!

Can we just drop them?

I'd be ok with dropping them at some point, perhaps it's ok to keep them for now (at least the cgroup ones). With Suggests is basically just metadata, so I don't think there's any option that will automatically install these.

[thaJeztah]

LGTM

(unless we strongly want these to be removed altogether)

[thaJeztah]

@cpuguy83 @silvin-lubecki @AkihiroSuda ptal

[tianon]

IMO these shouldn't be dropped completely yet -- aufs-tools is something folks should install if they still want to use aufs (which is deprecated, but still supported) and cgroupfs-mount is the type of things folks will need if their init system (or something else) doesn't set up cgroups for them, so I think there's still value in the communication these optional bits provide to users.

Once aufs is actually removed, then we should drop aufs-tools completely.

[silvin-lubecki]

LGTM

[thaJeztah]

Let's merge this 👍 🤗