change_uid = am_root && preserve_uid && st->st_uid != file->uid;
change_gid = preserve_gid && file->gid != GID_NONE
&& st->st_gid != file->gid;
change_uid = am_root && preserve_uid && st->st_uid != file->uid;
change_gid = preserve_gid && file->gid != GID_NONE
&& st->st_gid != file->gid;