completion: teach 'scissors' mode to 'git commit --cleanup='

Signed-off-by: SZEDER Gábor <szeder@ira.uka.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

contrib/completion/git-completion.bash

@@ -1110,7 +1110,7 @@ _git_commit ()
 
 	case "$cur" in
 	--cleanup=*)
-		__gitcomp "default strip verbatim whitespace
+		__gitcomp "default scissors strip verbatim whitespace
 			" "" "${cur##--cleanup=}"
 		return
 		;;