Teach simplify_away() and exclude_matches_pathspec() to handle struct
pathspec directly, eliminating the need for the struct path_simplify.
Also renamed the len parameter to pathlen in exclude_matches_pathspec()
to match the parameter names used in simplify_away().
Signed-off-by: Brandon Williams <bmwill@google.com> Reviewed-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>