git-submodule.sh: break overly long command lines

git-submodule.sh: break overly long command lines

For most of the subcommands of git-submodule(1), we end up passing a
bunch of arguments to the submodule helper. This quickly leads to overly
long lines, where it becomes hard to spot what has changed when one
needs to modify them.

Break up these lines into one argument per line, similarly to how it is
done for the "clone" subcommand already.

Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>