commit --strict feature request

Hi, i usually use bzr, and today i was searching for a commit --strict equivalent in git... i asked around and it seems there isn't one, so i'm writing this.

basically, by doing commit --strict it refuses to commit if there are untracked (and thus not ignored) files in the tree, this helps against forgetting to add new files (actually i find it so useful that i've even changed commit to be an alias to commit --strict in my bzr aliases )

greetings