baselen used to be the result of common_prefix() when it was made
builtin. Since 1d8842d (Add 'fill_directory()' helper function for
directory traversal - 2009-05-14), its value will always be
zero. Remove it because it's no longer variable.
Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>