git-commit: partial commit of paths only removed from the index

Because a partial commit is meant to be a way to ignore what are
staged in the index, "git rm --cached A && git commit A" should
just record what is in A on the filesystem.  The previous patch
made the command sequence to barf, saying that A has not been
added yet.  This fixes it.

Signed-off-by: Junio C Hamano <gitster@pobox.com>

git-commit.sh

@@ -404,7 +404,7 @@ t,)
 		(
 			GIT_INDEX_FILE="$NEXT_INDEX"
 			export GIT_INDEX_FILE
-			git update-index --remove --stdin
+			git update-index --add --remove --stdin
 		) || exit
 		;;
 	esac