Make the output order deterministic

[tavianator]

Fixes #63.

[sharkdp]

Minor: Maybe add a type annotation instead of collect::<T>() (just like below)

Suggested change

	let mut mapping = filetypes
	.mapping
	.iter()
	.map(|(filetype, category)| (filetype, theme.get_style(category)))
	.map(|(filetype, style)| style.map(|style| (filetype, style)))
	.collect::<Result<Vec<_>>>()?;
	let mut mapping: Result<Vec<_>> = filetypes
	.mapping
	.iter()
	.map(|(filetype, category)| (filetype, theme.get_style(category)))
	.map(|(filetype, style)| style.map(|style| (filetype, style)))
	.collect()?;

[tavianator]

It would be mapping: Vec<_> = ...collect()?;. But rustc's type inference doesn't actually handle that. I could do

let mut mapping: Vec<_> = ...collect::<Result<_>>()?;

but I figured I might as well put everything in one place

[sharkdp]

Thank you! If I understand correctly, the problem was that entries were previously just sorted by a single key? Now we sort by FileType in addition, which makes the sort order completely deterministic?

… and the rest is just a refactoring.

[tavianator]

Yeah the functional change is just

-filetypes_list.sort_unstable_by_key(|entry| entry.len());
+filetypes_list.sort_unstable_by_key(|entry| (entry.len(), entry));

Everything else is just refactoring.