better detection of file arguments

[sbidoul]

Currently, the client detects file arguments with a simple heuristics: an argument that does not start with - and corresponds to an existing file is considered a file argument.

This may break in rare situations where an existing file correspond to an argument name.

[foutoucour]

Hey @sbidoul did you consider cobra to manage the arguments ?
It seems a good tool. I used it for some cli here at Numigi. It was super easy.

[sbidoul]

Nope. Not sure it would help though. The problem is that we don't know (and don't want to reproduce) the exact cli of wkhtmltopdf. So I don't really know how to fix this bug, but it's probably not an issue in practice.