Originally the classic session replaced `gnome-shell.desktop` with
`gnome-shell-classic.desktop` (to add the --mode=classic parameter)
and added `nautilus-classic.desktop` (to force on desktop icons).
Neither is the case anymore (and hasn't been for years): Nowadays the
only expected difference is the GNOME_SHELL_SESSION_MODE variable and
the DesktopNames field, which are both set from the session .desktop
file rather than the gnome-session session definition.
Any difference in the latter - like not starting the USBProtection
plugin and missing systemd user session support - are bugs. The
easiest way to avoid those in the future is by removing the obsolete
duplication that enables them, so do just that.
https://gitlab.gnome.org/GNOME/gnome-shell-extensions/-/merge_requests/126
The overview is one of the defining features of GNOME 3, and thus
almost by definition at odds with the classic session, which
emulates a traditional GNOME 2 desktop.
Even with the less prominent placement inside the application menu
it never quite fit in - it doesn't help that besides the different
UI paradigma, the overview keeps its "normal" styling which differs
greatly with classic's normal mode.
So besides removing the "Activities" button via the session mode
definition, now that the apps-menu extension doesn't replace it anymore,
disable the overview completely in the classic session.
https://gitlab.gnome.org/GNOME/gnome-shell-extensions/merge_requests/69
Per-desktop overrides aren't limited to keys in org.gnome.mutter, so
we can use them instead of the alternate-tab extension to default to
the window switcher in the classic session.
https://bugzilla.gnome.org/show_bug.cgi?id=786496
GSettings now recognizes per-desktop overrides that can be used
to change schemas' default values for classic mode, so use that
instead of the separate override schema we currently use with
mutter's custom override mechanism.
https://bugzilla.gnome.org/show_bug.cgi?id=786496
