All pretty good points except I'd like to point out that asking an interactive y/n question is generally a bad idea in a command line app, especially if it's a

All pretty good points except I'd like to point out that asking an interactive y/n question is generally a bad idea in a command line app, especially if it's a superfluous question. A much better idea (if you're into this kind of hand-holding) would be to print out the command line that sets the default. Of course you wouldn't want to print this out every time, since it seems like a reasonable use case to not have a default, so you'd want to keep track and only print it the first time.