fsmonitor: use internal argv_array of struct child_process
Avoid magic array sizes and indexes by constructing the fsmonitor
command line using the embedded argv_array of the child_process. The
resulting code is shorter and easier to extend.
Getting rid of the snprintf() calls is a bonus -- even though the
buffers were big enough here to avoid truncation -- as it makes auditing
the remaining callers easier.
Inspired-by: Jeff King <peff@peff.net>
Signed-off-by: Rene Scharfe <l.s.r@web.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>