`just --usage` and `just --show` can not follow module path.

[groutoutlook]

I am using set unstable so thing can be a bit too out of scoped.. but there is this minor inconvenience when I'm trying to explore command:

> just --usage b
alias b := build
Usage: just b
> just --usage ../b
error: invalid module path `../b`

Same with --show flag. Can we make them follow module path if we set unstable?

Reproduce

• At current working dir.

set unstable
set fallback

alias b := build
build: 
	# anything here

• Parent dir

set unstable
set fallback

alias b := build
build: 
	# different thing.