submodule: preserve all arguments exactly when recursing

submodule: preserve all arguments exactly when recursing

Shell variables only hold strings, not lists of parameters,
so $orig_args after

        orig_args="$@"

fails to remember where each parameter starts and ends, if
some include whitespace.  So

        git submodule update \
                --reference='/var/lib/common objects.git' \
                --recursive --init

becomes

        git submodule update --reference=/var/lib/common \
                objects.git --recursive --init

in the inner repositories.  Use "git rev-parse --sq-quote" to
save parameters in quoted form ready for evaluation by the
shell, avoiding this problem.

Helped-By: Jonathan Nieder <jrnieder@gmail.com>
Signed-off-by: Kevin Ballard <kevin@sb.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>