parse-options: rearrange long_name matching code
Move the code for handling a full match of long_name first and get rid
of negations. Reduce the indent of the code for matching abbreviations
and remove unnecessary curly braces. Combine the checks for whether
negation is allowed and whether arg is "n", "no" or "no-" because they
belong together and avoid a continue statement. The result is shorter,
more readable code.
Signed-off-by: René Scharfe <l.s.r@web.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>