doc: check for absence of the form --[no-]parameter

For better searchability, this commit adds a check to ensure that parameters
expressed in the form of `--[no-]parameter` are not used in the
documentation.  In the place of such parameters, the documentation should
list two separate parameters: `--parameter` and `--no-parameter`.

Signed-off-by: Jean-Noël Avila <jn.avila@free.fr>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Documentation/git-index-pack.adoc

@@ -36,7 +36,8 @@ OPTIONS
 	fails if the name of packed archive does not end
 	with .pack).
 
---[no-]rev-index::
+--rev-index::
+--no-rev-index::
 	When this flag is provided, generate a reverse index
 	(a `.rev` file) corresponding to the given pack. If
 	`--verify` is given, ensure that the existing