Tasksel: how to create custom tasks?

[Christian Perrier <bubulle@debian.org>]

(please keep christian.perrier@onera.fr CC'ed to answers as I'm
currently out of access to my Debian mail)

I'm certainly missing something important...or misunderstanding things
about tasksel.

I'm currently trying to setup an automated install process for future
desktop machines here at work.

So, I thought about using a custom tasksel task for that.

Tasksel README mentions one can either create a custom .desc file and
drop it into /usr/share/tasksel, or modify debian-tasks.desc.

My first try was with the second method.

I have created a "ONERA" task (file named "onera" in tasks/):

Task: onera
Relevance: 8
Section: user
Description: ONERA
 This task provides software for ONERA purposes.
Key:
  x-window-system-core
  gnome-desktop-environment
Packages:
  gdm
  gnome
  xscreensaver
  fortune-mod
  menu
  mozilla-browser
  mozilla-psm
  mozilla-xft
  xprt-xprintorg 
  gimp
  openoffice.org-bin
  openoffice.org
  openoffice.org-help-en
  mozilla-firefox
  mozilla-thunderbird
  mozilla-thunderbird-offline
  gimp


As one may see, the task is close to "desktop", with a few more
packages.

When building tasksel, nothing bad happens and I end up with
debian-tasks.desc with this, among other entries:

Task: onera
Section: user
Relevance: 8
Description: ONERA
 This task provides software for ONERA purposes.
Key: 
  x-window-system-core
  gnome-desktop-environment
Packages: task-fields

....and this task indeed installs nothing among gnome/mozilla/gimp
stuff. Running tasksel manually and selecting it just installs nothing.

The README file says about "Packages:":

The Packages field tells how to get a complete list of packages that are in
the task. In the example above, it uses the task-fields method, which is
built into tasksel, and looks for Task fields in the control data of available
packages, that list the name of the task. It's also possible to define
other methods, by adding programs to /usr/lib/tasksel/packages/. Then


I understand this as : "tasksel will look in Packages files and search
those with "Task: onera"....which means why it finds none...and thus
installs none.

How can I really build my own custom task?

I'm pretty sure I'm deeply misunderstanding something about tasks, but
it's quite confusing to me..:-)