Bug#1018076: transition: gjs and gnome-shell likely to be removed from armel

[Simon McVittie <smcv@debian.org>]

On Wed, 31 Aug 2022 at 10:19:18 +0100, Simon McVittie wrote:
> I think we'll probably want to swap from a mozjs91-based gjs to a
> mozjs102-based gjs either before or during the mutter/Shell transition
> (#1018118)

I'm having trouble finding the right arguments for `dak rm -n`, but I
think the transition will go something like this:

0. Adapt some packages to stop depending on gjs or gnome-shell on armel:
   - gdm3 - fixed in 42.0-2 (experimental)
   - glade - fixed in 3.40.0-2, might need additional changes if
     the autopkgtest fails on armel as a result of removing gjs support
   - ibus - #1018871 reported
   - libguestfs - #1018819 reported
   - libportal - fixed in 0.6-3
   - libsecret - fixed in 0.20.5-3
   - ostree - fixed in 2022.5-3
1. Wait for release team ack
2. Upload gjs/experimental and gdm3/experimental to unstable
3. Adapt meta-gnome3 so gnome-core and gnome are only built on
   architectures that have a working gjs
4. Remove only these armel *binaries* (as NBS), leaving the rest of their
   source packages intact:
   - gdm3 (from src:gdm3)
   - gnome-core (from src:meta-gnome3)
   - gnome (from src:meta-gnome3)
6. Remove all binaries of these source packages from armel:
   - clapper
   - eos-sdk
   - gjs
   - gnome-books
   - gnome-characters
   - gnome-maps
   - gnome-shell
   - gnome-shell-extension-manager
   - gnome-shell-extension-panel-osd
   - gnome-shell-mailnag
   - gnome-shell-pomodoro
   - gnome-sushi
   - gpaste
   - polari
7. Release team will need to force through the transition by ignoring the
   "all task packages are installable" check on armel, because
   task-gnome-desktop will now be uninstallable on armel

Unfortunately `dak rm -R -n -aarmel` seems to still be showing packages like
libportal, libsecret and ostree as having B-D on gjs, even though the B-D
in question is now qualified with an architecture list that excludes armel.
I think these are now false positives.

I think we can safely ignore these packages, which have Build-Depends
(not Build-Depends-Indep!) on gjs and therefore are not ignored by
dak rm -R -n -A -aarmel, but only build Architecture: all binaries:

- arc-theme
- foliate
- gnome-sound-recorder
- gnome-weather

Contingency plan if #1018819 in libguestfs is not fixed is to also remove
all binaries built by these sources from armel:

- guestfs-tools
- kworkflow
- lava
- libguestfs
- libnbd
- nbdkit
- oz
- poke
- supermin
- virt-p2v
- virt-v2v

and ignore diffoscope's Build-Depends: python3-guestfs (which should
arguably be B-D-I).

Contingency plan if #1018871 in ibus is not fixed is probably a NMU.
Lots of libraries depend on libibus-1.0-dev, so removing ibus from armel
would be very disruptive.

    smcv