rebase: remove useless arguments check

Remove a check on the number of arguments for --onto and -x options.
It is not possible for $# to be <= 2 at this point :

 - if --onto or -x has an argument, git rev-parse --parseopt will
   provide something like this :
     set -- --onto 'x' --
   when parsing the "--onto" option, $# will be 3 or more if there are
   other options.

 - if --onto or -x doesn't have an argument, git rev-parse --parseopt
   will exit with an error and display usage information.

Signed-off-by: Nicolas Vigier <boklm@mars-attacks.org>
Signed-off-by: brian m. carlson <sandals@crustytoothpaste.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

git-rebase.sh

@@ -238,12 +238,10 @@ do
 		action=${1##--}
 		;;
 	--onto)
-		test 2 -le "$#" || usage
 		onto="$2"
 		shift
 		;;
 	-x)
-		test 2 -le "$#" || usage
 		cmd="${cmd}exec $2${LF}"
 		shift
 		;;