parse-options: allow positivation of options starting, with no-

parse-options: allow positivation of options starting, with no-

Long options can be negated by adding no- right after the leading
two dashes. This is useful e.g. to override options set by aliases.

For options that are defined to start with no- already, this looks
a bit funny. Allow such options to also be negated by removing the
prefix.

The following thirteen options are affected:

	apply          --no-add
	bisect--helper --no-checkout
	checkout-index --no-create
	clone          --no-checkout --no-hardlinks
	commit         --no-verify   --no-post-rewrite
	format-patch   --no-binary
	hash-object    --no-filters
	read-tree      --no-sparse-checkout
	revert         --no-commit
	show-branch    --no-name
	update-ref     --no-deref

The following five are NOT affected because they are defined with
PARSE_OPT_NONEG or the non-negated version is defined as well:

	branch       --no-merged
	format-patch --no-stat             --no-numbered
	update-index --no-assume-unchanged --no-skip-worktree

Signed-off-by: Rene Scharfe <rene.scharfe@lsrfire.ath.cx>
Signed-off-by: Junio C Hamano <gitster@pobox.com>