While the extension system already uses an XDG location (XDG_CONFIG_HOME),
other components use the deprecated $HOME/.gnome2 directory.
Replace both with XDG_DATA_HOME - the existing data (app usage stats,
looking glass history and extensions) is not migrated to the new location.
https://bugzilla.gnome.org/show_bug.cgi?id=617555
Consumer documentation will live at http://live.gnome.org/GnomeShell/Extensions
In terms of implementation; basically we load extensions from the well-known
directories. Add a GConf key to disable extensions by uuid. There is a new
option --create-extension for the gnome-shell script which takes a bit of
interactive input, sets up some sample files, and launches gedit.
No extensions UI in this patch; that will come later.
https://bugzilla.gnome.org/show_bug.cgi?id=599661
