version of alias that checks that missing_blocks is empty

[David Craven]

It should be pretty easy to add a version of alias that only succeeds in the case that the dag is complete.

[Rüdiger Klaehn]

why do you need it? Can you not just check if there are any missing links and then abort if that is not the case?

[David Craven]

I guess you'd have to alias it first and then check, but sounds reasonable