strip: drop -b/--backup option (BC) This option had very limited utility and counterintuitive behavior and collided unfortunately with the much later -B option. Normally we would no-op such a feature so as to avoid annoying existing scripts. However, we have to weigh that against the silent misbehavior that results when users mistakenly intended to use -B: because -b takes no arg, the bookmark gets interpreted as a normal revision, and gets stripped without removing the associated bookmark, while also not backing up the revision in question. A no-op behavior or warning would only remove the latter half of the misadventure. The only users I can find of this feature were using it in error and have since stopped. The few (if any) remaining users of this feature would be better served by --no-backup.