Hi,

i attached patch with new variable(tracker) for gnome.scm.

Tracker, is a search engine and metadata storage system used for 
nautilus(gnome file manager).

The steps i follow are:

  a) I edit gnu/packages/gnome.scm and added tracker variable.
  b) git add gnu/packages/gnome.scm
  c) git commit -m 'gnu: Add tracker.'
  d) git format-patch -1

i wait your comments. Regards.