Add canonicalise paths to snapshots

[Danil42Russia]

Our project has its own wrappers for loading and comparing the programme output with a snapshot. It looks something like this:

fn assert_snapshot_matches(&self, snapshot_test_path: &str) -> &Self {
    let assertion = assertion();
    let normalized = self.get_normalized_stdout();

    let mut snapshot_path = std::env::current_dir()?;
    snapshot_path.push(snapshot_test_path);

    let expected = Data::read_from(&snapshot_path, None);
    assertion.eq(normalized, expected);
    self
}

However, sometimes the symbol for transitioning to the parent directory .. may appear in the paths to the snapshot. Because of this, when submitting tests, you may see the following

---- expected: tests/integration/../integration/snapshots/snapshot_name.stdout.txt
++++ actual:   In-memory

How about adding Path::canonicalize to the call, where you save the snapshot?

snapbox/crates/snapbox/src/data/source.rs

Lines 14 to 18 in c461f19

	pub fn path(path: impl Into<std::path::PathBuf>) -> Self {
	Self {
	inner: DataSourceInner::Path(path.into()),
	}
	}

But in Windows, truncating the current directory may break due to UNC paths :(

snapbox/crates/snapbox/src/dir/ops.rs

Lines 219 to 230 in c461f19

	pub(crate) fn display_relpath(path: impl AsRef<std::path::Path>) -> String {
	let path = path.as_ref();
	let relpath = if let Ok(cwd) = std::env::current_dir() {
	match path.strip_prefix(cwd) {
	Ok(path) => path,
	Err(_) => path,
	}
	} else {
	path
	};
	relpath.display().to_string()
	}

[epage]

In general, UNC paths shouldn't be shown to users. There are libraries like dunce which we use but under an unrelated feature and we'd have to weigh the benefits of that dependency against the visual noise.

[Danil42Russia]

Yes, I completely agree with you. I thought about it several times and it seems that we can do without dunce.
The main thing is to trim UNC when outputting in diff mode, and if UNC appears somewhere else, it's not a big deal to some extent