> 2. WHy would a user wish to *restore* the old cache
> ?  If the user has downloaded more than they have
> previously, then it makes sense to keep the current
> one.. Likewise, if they have downloaded less than
> the previous, then the user can just do an "Update
> existing"
If the user has downloaded more than the previous, then it makes sense to keep
the current.
If the user didn't, then using the new cache will require redownloading all
files that was listed in the old cache but not in the new. If you cancel just
after starting, then using the new is essentially a new mirror, not an
update.
Further more, cancel is broken. All files not mirrored get deleted. Don't
cancel, don't kill the program by shutting down. Just pause, hibernate if
necessary, resume later.