rev-parse parseopt: interpret any whitespace as start of help text

rev-parse parseopt: interpret any whitespace as start of help text

Currently, rev-parse only interprets a space ' ' character as the
delimiter between the option spec and the help text.  So if a tab
character is placed between the option spec and the help text, it will
be interpreted as part of the long option name or as part of the arg
hint.  If it is interpreted as part of the long option name, then
rev-parse will produce what will be interpreted as multiple arguments
on the command line.

For example, the following option spec (note: there is a <tab> between
"frotz" and "enable"):

    frotz	enable frotzing

will produce the following set expression when --frotz is used:

    set -- --frotz --

instead of this:

    set -- --frotz  enable --

Mark t1502.2 as fixed.

Signed-off-by: Brandon Casey <drafnel@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>