[PATCH 4/3] parse-options: disallow --no-no-sth

["René Scharfe" <rene.scharfe@lsrfire.ath.cx>]

Now that options whose definition starts with "no-" can be negated
by removing said "no-", there is no need anymore to allow them to
be negated by adding a second "no-", which just looks silly.

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

E.g., with this patch --no-add and --add (its reverse) are still
accepted by git apply, but --no-no-add isn't anymore.

Suggested-by: Junio C Hamano <gitster@pobox.com>
Signed-off-by: Rene Scharfe <rene.scharfe@lsrfire.ath.cx>
---
 parse-options.c          |    3 +++
 t/t0040-parse-options.sh |    4 ++--
 2 files changed, 5 insertions(+), 2 deletions(-)

diff --git a/parse-options.c b/parse-options.c
index 1908996..dc59bba 100644
--- a/parse-options.c
+++ b/parse-options.c
@@ -248,6 +248,9 @@ is_abbreviated:
 				}
 				continue;
 			}
+			/* double negation? */
+			if (!prefixcmp(long_name, "no-"))
+				continue;
 			flags |= OPT_UNSET;
 			rest = skip_prefix(arg + 3, long_name);
 			/* abbreviated and negated? */
diff --git a/t/t0040-parse-options.sh b/t/t0040-parse-options.sh
index a44bcb9..b124f3c 100755
--- a/t/t0040-parse-options.sh
+++ b/t/t0040-parse-options.sh
@@ -101,11 +101,11 @@ test_expect_success 'OPT_BOOL() #5' 'check boolean: 1 -B'
 test_expect_success 'OPT_BOOL() is idempotent #1' 'check boolean: 1 --yes --yes'
 test_expect_success 'OPT_BOOL() is idempotent #2' 'check boolean: 1 -DB'
 
-test_expect_success 'OPT_BOOL() negation #1' 'check boolean: 0 -D --no-yes'
-test_expect_success 'OPT_BOOL() negation #2' 'check boolean: 0 -D --no-no-doubt'
+test_expect_success 'OPT_BOOL() negation' 'check boolean: 0 -D --no-yes'
 
 test_expect_success 'OPT_BOOL() no negation #1' 'check_unknown --fear'
 test_expect_success 'OPT_BOOL() no negation #2' 'check_unknown --no-no-fear'
+test_expect_success 'OPT_BOOL() no negation #3' 'check_unknown --no-no-doubt'
 
 test_expect_success 'OPT_BOOL() positivation' 'check boolean: 0 -D --doubt'
 
-- 
1.7.9.2