ls: Use case-insensitive comparison for filenames

[hbina]

hbina@akarin:~/git/uutils$ git checkout main 
Switched to branch 'main'
Your branch is up to date with 'origin/main'.
hbina@akarin:~/git/uutils$ diff <(ls --color=never) <(cargo run --quiet -- ls)
1,3d0
< build.rs
< Cargo.lock
< Cargo.toml
5a3,4
> Cargo.lock
> Cargo.toml
7,8d5
< docs
< examples
13a11,13
> build.rs
> docs
> examples
hbina@akarin:~/git/uutils$ git checkout hbina-ls-sort-using-lowercase 
Switched to branch 'hbina-ls-sort-using-lowercase'
hbina@akarin:~/git/uutils$ diff <(ls --color=never) <(cargo run --quiet -- ls)

Signed-off-by: Hanif Ariffin hanif.ariffin.4326@gmail.com

[tertsdiepraam]

Hi! So, we've done things like this before and the result was this issue: #2149

The short version is, sorting by name is dependent on locale and requires unicode collation, for which there are no good crates that I'm aware of right now. The current sorting in ls is based on the C locale. So we cannot merge this as is, but we could make a first step towards some localization. We could for instance sort case-insensitively if the locale is not C.

[tertsdiepraam]

In the long term, I think we should use icu4x for all this unicode stuff, but they don't have a collator yet (unicode-org/icu4x#971). In the meantime, we could use rust_icu_ucol, which is a wrapper around the C ICU library.