git-gui: deal with unknown files when pressing the "Stage Changed" button
As a shortcut the "Stage Changed" button can be used to stage all current
changes in the worktree which are not set to ignore. Previously unknown
files would be ignored. The user might want to say: "Just save everything
in my worktree". To support this workflow we now ask whether the user also
wants to stage the unknown files if there are some present.
Signed-off-by: Heiko Voigt <hvoigt@hvoigt.net>
Signed-off-by: Pat Thoyts <patthoyts@users.sourceforge.net>