Emacs next variants

[Cayetano Santos <csantosb@inventati.org>]

Hi guix,

  As for today, the inheritance of emacs, master branch, variants is as
  follows

    (emacs-next-tree-sitter (emacs-next-gtk (emacs-next (emacs))))

  Having tree-sitter is really useful, but optional, and doesn’t produce
  any harm to users. They may opt to use it, or not.

  This is not the case of the gtk variant. If one wants to use
  tree-sitter, the gtk variant is mandatory. When under x server, this
  produces a welcome warning advising about unattended effects, crashes,
  and leak of support when combining gtk emacs with x server.

  So, is there any reason for this dependency chain ? Why not ?

    (emacs-next-gtk (emacs-next-tree-sitter (emacs-next (emacs))))

Best,

Cayetano