Tab Completion will complete positional arg when there is no completer function

[Rudedog9d]

Lets take the command tail [-n NUM] FILE as an example:

Whenever a optional argument (-n) with a value (NUM) exists and is tab completed, pypsi checks for a callback to get the value for NUM. Because a callback doesn't exist, the current behavior (wrongly) assumes that the option -n does not have a value, and tries to complete FILE instead of waiting for NUM to be consumed

Possible Solutions

1. Improve the way optional args tab-complete
2. Make sure optional args always have a callback (ex, default to completer=lamba x,y,z: [] to return an empty list)