[PATCH 3/3] Add git-ls-files -k.

[PATCH 3/3] Add git-ls-files -k.

When checkout-cache attempts to check out a non-directory where
a directory exists on the work tree, or to check out a file
under directory D when path D is a non-directory on the work
tree, the attempt fails.  Before running checkout-cache, the
user can run git-ls-files with the -k (killed) option to get a
list of such paths.  The tagged output format uses "K" to denote
them.  This is useful for Porcelain layer to be careful when
dealing with the recently corrected behaviour of checkout-cache.

Signed-off-by: Junio C Hamano <junkio@cox.net>
Signed-off-by: Petr Baudis <pasky@ucw.cz>