Autocomplete for files doens't work on folders.

[Lexer747]

$ acci-ping drawframe ./gr<tab>

This should complete to

graph/

Currently it just returns "".

[Lexer747]

Autocomplete also doesn't work when cursor is mid string.

$ acci-ping drawframe -<tab>  ./graph/data/testdata/input/huge-over-days.pings

Should complete to the flags of drawframe instead if just returns "".