Ah, duh. Interesting observation of the UI. A line comment in the pull request looks more like a comment on the previous diff block.

If we moved the check for a missing input file to Invoke, then it would have to reach back and instantiate Options again to print the usage. I think we should leave the check for the missing input file here, but we should check that the input file exists in Invoker (since we don't need to print the usage in that case...just write an error that the file is bogus).

Either way, that's just polishing...so not a blocker.