APPLIED: [REVIEW][Unstable] Introduce variant support for master kernel packages

[Seth Forshee]

On Tue, Dec 03, 2019 at 04:26:34PM -0600, Seth Forshee wrote:
> For some backport packages in bionic we've adopted a scheme where
> package names include the upstream version (e.g. linux-azure-5.3,
> linux-meta-azure-5.3, etc.). For these packages a list of the variants
> supported from the package (e.g. -edge) is used by linux-meta to
> determine what meta packages need to be produced. This allows changing
> the variant without rebuilding the kernel.
> 
> This has utility for the master kernels during development. We would be
> able to introduce new kernel verions into the -proposed and -release
> pockets earlier for testing while keeping the primary variant packages
> at a better-tested kernel versions. The meta packages would be suffixed
> with the variant, such as -wip as used in the patches which follow,
> allowing e.g. linux-generic-wip to be installed for testing the
> work-in-progress kernel.
> 
> Variant support is also likely to be useful after development, easing
> the transition of hwe and hwe-edge to newer kernel version, for example.
> 
> Supporting variants is more complicated for the master kernel than for
> derivatives. There are a handful of packages which should only produces
> by the master kernel, such as linux-libc-dev, so the kernel source
> package needs to be aware of variants to know whether or not to produce
> these packages. linux-restricted-modules also produces meta packages,
> which need to include variant suffixes. Therefore all packages will gain
> a $DEBIAN/variants file. The list of variants for a given source package
> will be maintained in kernel-series.yaml and updates by cranky-fix.
> 
> I'd appreciate review on the following patches for unstable which
> implement variant support and prepare the packaging for including
> upstream version numbers in the source package names. There are also
> some cleanup patches. For the kernel package I've included an example of
> changing the source package name from linux to linux-5.4. I did not
> include patches changing the source package name for supporting
> packages; these will be done when preparing new uploads.
> 
> I will point out that there are inconsistencies in the format of
> substition variables for control files in these patches. This is because
> it is inconsistent in our packaging. I used the format which seemed to
> be predominant for each package. These should be unified, but I did not
> do so as part of this work.
> 
> I've got a test build using these changes and new source package names
> at https://launchpad.net/~sforshee/+archive/ubuntu/test-builds.

Applied to focal/master-next, with adjustment to use SRCPKGNAME as
requested by Andy.