You can use short mode of git status (see man git-status(1)), which gives the following output:
Without short mode:
$ git status
...
# Untracked files:
# (use "git add <file>..." to include in what will be committed)
#
# README
# application/libraries/Membres_exception.php
no changes added to commit (use "git add" and/or "git commit -a")
With short mode:
$ git status -s
M application/models/membre_model.php
?? README
?? application/libraries/Membres_exception.php
Then using grep, awk and xarg, you can add the files where the first column is ??
.
$ git status -s | grep '??' | awk '{ print $2 }' | xargs git add
and see that it worked:
$ git status
# On branch new
# Changes to be committed:
# (use "git reset HEAD <file>..." to unstage)
#
# new file: README
# new file: application/libraries/Membres_exception.php