spec: Add progress option

[ghost]

Is it possible to add an option to show the progress?
If you implement it, you should not display it by default according to Unix philosophy.

[codesoap]

I think the most UNIX way to do this would be to utilise pv:

pv mydata | age -r age1df9vthfpykfsd4teaehwau7q8pt0f8d6sad22dgerqamnd43t32qzv54e5 -o mydata.age

[FiloSottile]

Yeah I recommend using pv for progress monitoring. It's the beauty of UNIX composable tools!