bug#23196: [Hunting bug#23196]: GNOME "Sharing" settings is blank

[Leo Prikler <leo.prikler@student.tugraz.at>]

Hi simon,

The Sharing dialog now consists of two buttons, which at least change
some settings, along with the text field, that is still blank.  That
being said, I am far from able to assert, that this functions as
intended; apparently, there should be more settings[1], and those that
we do have don't seem to work either.

The currently available settings depend on gnome-user-share(1) and
rygel(2).  
(1) should be accessible via dav://$HOSTNAME, where $HOSTNAME is the
host name you've configured in /etc/config.scm plus ".local" in most
cases.  It seems to rely on apache or httpd; either way, starting it
manually doesn't work and changing the settings doesn't seem to do
anything.  Attempting to connect to this server (that isn't spawned)
yields an "invalid argument" error.
(2) can be started manually, but is not started automatically through
the settings dialog.  It seems like rygel actively listens to changes
on $XDG_CONFIG_HOME/rygel.conf, however, which is where GNOME stores
those settings.  In other words it would be possible to circumvent this
issue through a shepherd user service. 
To access the media, a UPnP-capable media player such as VLC or device
is required.  I fear we don't ship anything like that with our gnome-
desktop-service.

On a related note, the tracker service, which is required by GNOME
Music and optional for rygel seems to be missing and manually starting
it while having tracker enabled in (2) leads to a trap instruction.  

Regards,
Leo

[1] https://wiki.gnome.org/Design/OS/Sharing