runit-dbus-user-session looks like it is meant to provide essentially
the same semantics as `systemd --user` + dbus-user-session, but with
runit replacing systemd as the service manager:

* on first login of e.g. uid 1000, a service manager and an instance
  of `dbus-daemon --session` start
* user processes inherit a suitable $XDG_RUNTIME_DIR and
  $DBUS_SESSION_BUS_ADDRESS, canonically /run/user/$uid and
  unix:path=/run/user/$uid/bus respectively
* the second and subsequent parallel logins of uid 1000 share that bus
  instead of starting a new one
* after the last logout of uid 1000, the service manager and the
  dbus-daemon both exit

Is that true? If yes, it should probably have Provides:
dbus-session-bus, making it possible to use as a drop-in replacement
for dbus-user-session or dbus-x11 and to satisfy the dependencies of
the many packages that need a working session bus.

Thanks,
    smcv