git-rev-list.txt: prune options in synopsis

git-rev-list.txt: prune options in synopsis

The synopsis section in git-rev-list.txt has grown to be a huge list
that probably needs its own synopsis. Since the list is huge, users may
be given the false impression that the list is complete, however it is
not. It is missing many of the available options.

Since the list of options in the synopsis is not only annoying but
actively harmful, replace it with `[<options>]` so users know to
explicitly look through the documentation for further information.

While we're at it, update the optional path notation so that it is more
modern.

Signed-off-by: Denton Liu <liu.denton@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>