Add read_dir to mod_util::Mod (#232)

[redruin1]

Implements the proposed function. Needs testing, however.

[redruin1]

Notably, the function here returns a Result<Vec<ModEntry>>, where each ModEntry has a path() and is_file/dir() methods. This slightly changes the syntax from before; e.g:

let mod: Mod = ...;

let cfg_files = mod.read_dir("locale/en")?.iter()
    .filter(|&x| x.is_file() && x.path().extension() == Some("cfg"));

for cfg_file in cfg_files {
    let data = mod.read_file(&cfg_file.path())?;
    // ...
}

The returned value should probably be an iterator instead of a Vec, but I'm too smoothbrained with Rust to be able to do that at the moment.

[fgardt]

This looks nice for a start. One thought I have is that instead of returning a Vec<ModEntry> we could have a new struct like ModDir that then also implements Iterator so its usage would be very similar to the regular fs::read_dir.

[fgardt]

The CI test report failing is weird but not a blocker, the clippy lints would be nice to solve tho.

[fgardt]

The returned value should probably be an iterator instead of a Vec, but I'm too smoothbrained with Rust to be able to do that at the moment.

oh I just read this now, if you're fine with it I'll clean the PR up and change it into the iterator like I proposed.

[redruin1]

Switched branch to make tracking easier. Implemented the iterator, no idea if it's "proper", but the compiler doesn't complain.

I want to write some tests to make sure it actually behaves, ideally with some actual mod folders/zips. Whats the rusty way to do this? Should I make a mod_util/test folder and write some code to try and read some example mods in that folder?

[fgardt]

Switched branch to make tracking easier. Implemented the iterator, no idea if it's "proper", but the compiler doesn't complain.

I have not checked through it yet, my own implementation approach got a bit stuck at some point.

I want to write some tests to make sure it actually behaves, ideally with some actual mod folders/zips. Whats the rusty way to do this? Should I make a mod_util/test folder and write some code to try and read some example mods in that folder?

For the blueprint and prototypes crates I made separate folders for tests BPs / data.raw dumps and put the things in there so in this case I guess we could have a test_mods folder under mod_util/test_mods that would contain different test mods. The actual test code itself can be in the same file at the bottom in a tests module (see the rust book on how to write tests).