option -q not passed from "git commit" to "git gc --auto"

Hello,

It seems that when "git commit" is run with the "-q" option, there are
still, from time to time, messages that get printed. With the French
locale the message is:
  Compression automatique du dépôt en tâche de fond pour optimiser les performances.
  Voir "git help gc" pour toute information sur le nettoyage manuel.

From what I could guess, this is due to the fact that "git commit" calls "git gc --auto", but does not propagate the "-q" option if present.

A similar problem was present some time ago with "git fetch" and was solved in the 2-line patch 6fceed3b . I guess that the same should be done for "git commit".

Regards, Pierrick