feat(cli): default to XDG_CONFIG_HOME if set

[michaelBelsanti]

Uses $XDG_CONFIG_HOME/rustscan.toml if it is set, falls back to ~/.rustscan.toml otherwise.

[michaelBelsanti]

closes #741

[PsypherPunk]

I think I'm generally in favour of this (and we can update the wiki to reflect limited support for the XDG spec.) but it'd be good to wrap this in a unit test.

We're currently using nextest which, according to their docs, allows altering "the environment within tests"; however, while that's fine for our CI environment, we can't guarantee that end users won't run cargo test and the resulting effect on their environment variables.

Thoughts?

[PsypherPunk]

Incidentally, poking around a little more, Go's xdg package "uses Known Folders as defaults" for Windows, FWIW.

[michaelBelsanti]

Incidentally, poking around a little more, Go's xdg package "uses Known Folders as defaults" for Windows, FWIW.

Thanks, I'll look into using that.

I think I'm generally in favour of this (and we can update the wiki to reflect limited support for the XDG spec.) but it'd be good to wrap this in a unit test.

Can you explain a bit what this would entail? I don't do much coding outside scripting, so not very familiar with unit testing.

[bee-san]

IMO use Dirs https://crates.io/crates/dirs which is made for this :)