Docs: Use "-l::\n--long\n" format in OPTIONS sections

Docs: Use "-l::\n--long\n" format in OPTIONS sections

The OPTIONS section of a documentation file contains a list
of the options a git command accepts.

Currently there are several variants to describe the case that
different options (almost) do the same in the OPTIONS section.

Some are:

 -f, --foo::
 -f|--foo::
 -f | --foo::

But AsciiDoc has the special form:

 -f::
 --foo::

This patch applies this form to the documentation of the whole git suite,
and removes useless em-dash prevention, so \--foo becomes --foo.

Signed-off-by: Stephan Beyer <s-beyer@gmx.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>