Previously, some calls lookup_untracked would pass a full path. But
lookup_untracked assumes that the portion of the path up to and
including to the untracked_cache_dir has been removed. So
lookup_untracked would be looking in the untracked_cache for 'foo' for
'foo/bar' (instead of just looking for 'bar'). This would cause
untracked cache corruption.
Instead, treat_directory learns to track the base length of the parent
directory, so that only the last path component is passed to
lookup_untracked.
Helped-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com> Signed-off-by: David Turner <dturner@twopensource.com> Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>