fix 'git update-index --verbose --again' output

'git update-index --verbose' consistently reports paths relative to the
work-tree root. The only exception is the '--again' option, which reports
paths relative to the current working directory.

Change do_reupdate to use non-prefixed paths.

Signed-off-by: Karsten Blees <blees@dcon.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

builtin/update-index.c

@@ -579,7 +579,7 @@ static int do_reupdate(int ac, const char **av,
 		 * or worse yet 'allow_replace', active_nr may decrease.
 		 */
 		save_nr = active_nr;
-		update_one(ce->name + prefix_length, prefix, prefix_length);
+		update_one(ce->name, NULL, 0);
 		if (save_nr != active_nr)
 			goto redo;
 	}