PackageKit session interface moving from gnome-packagekit to gnome-software

[Richard Hughes <hughsient gmail com>]

Hi all,

Matthias asked me to post here, I hope it's okay. The plan for 3.16 is
to move completely the _session_ dbus helper interface from
gnome-packagekit to gnome-software. There are many reasons, one of the
biggest being that the gnome-packagekit code is super hard to maintain
(originally libdbus now crufty dbus-glib) and that we don't want to
have two session processes just sitting around in case the user
software calls a helper method.

The other reasons include things like needing to break the interface
for wayland support (no XIDs anymore) although that's a mail for
another day, and also that we can leverage a lot of the nice UX
patterns we have developed for gnome-software. Giant modal dialogs
with no parent popping up a few minutes after starting an application
should be a thing of the past.

I know GNOME doesn't have a policy of supporting other desktops
dicing-and-slicing the tarballs to make a derivative, but there are a
few small distros that don't ship the appstream-metadata required by
gnome-software. I'm happy to help them, and we already support quite a
lot of other distros just using appstream-builder. GNOME Software
should also still work as a helper service, although if a distro still
wants to ship the session dbus interface without the full software
shell, they could just ship a package with the .desktop file set to
NoDisplay=true.

I'm not going to add a --enable-legacy-dbus-service as I don't want to
support the matrix of both session things supporting the same
interface, and doing that would make old untested and crufty code
bit-rot even further and complicate debugging. Comments welcome,

Richard