unpack-trees: do not muck with attributes when we are not checking out

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

unpack-trees.c

@@ -87,7 +87,8 @@ static int check_updates(struct unpack_trees_options *o)
 		cnt = 0;
 	}
 
-	git_attr_set_direction(GIT_ATTR_CHECKOUT, &o->result);
+	if (o->update)
+		git_attr_set_direction(GIT_ATTR_CHECKOUT, &o->result);
 	for (i = 0; i < index->cache_nr; i++) {
 		struct cache_entry *ce = index->cache[i];
 
@@ -112,7 +113,8 @@ static int check_updates(struct unpack_trees_options *o)
 		}
 	}
 	stop_progress(&progress);
-	git_attr_set_direction(GIT_ATTR_CHECKIN, NULL);
+	if (o->update)
+		git_attr_set_direction(GIT_ATTR_CHECKIN, NULL);
 	return errs != 0;
 }