Use shell autocompletion for filling in placeholders

[xeruf]

Idk how feasible this is, but interactively typing paths & co is tedious, maybe shell tab-completion can be leveraged somehow...

[isacikgoz]

This may be a good QoL improvement but in the current state it will take my considerable time to implement it. And apparently I can't find enough time to take care of the project. I'll leave this open as a feature request and who knows maybe somebody would like to add this feature.