Support different example inputs for part 1 and part 2 in tests

[snorremd]

First of all, thank you for an amazing starter template. This repo makes it so easy to try out Rust for advent of code!

In AOC 2023 the first day puzzle has two example inputs, one for each part. The default read_file function only accepts a day which is strongly typed so you can only ever read 01.txt, etc.

In my project I just added a new function that takes a part number too:

pub fn read_file_part(folder: &str, day: Day, part: u8) -> String {
    let cwd = env::current_dir().unwrap();
    let filepath = cwd.join("data").join(folder).join(format!("{day}-{part}.txt"));
    let f = fs::read_to_string(filepath);
    f.expect("could not open input file")
}

[fspoettel]

Hi @snorremd, thanks for bringing this up. I like the idea, we should definitely have something like this. What do you think about 01.txt and 01-2.txt as a convention? Then the scaffolded file for part 1 would not have to be renamed.

edit: hmm file order might be a problem here.