This commit is a tiny win in compiled code size of a final binary
including `clap` which shaves off 19k of compiled code locally.
Previously tokens were checked if they were a number by using
`.parse::<f64>().is_ok()`, but parsing floats is relatively heavyweight
in terms of code size. This replaces the check with a more naive "does
this string have lots of ascii digits" check where the compiled size of
this check should be much smaller.
We are doing direct transmutes between `OsStr` and `[u8]`.
https://github.com/rust-lang/rust/pull/95290 would make this natively
supported but I got tired of waitin for it.
This only saves about 1/4s off of `cargo build`.
This took 2.9 KiB off of `cargo bloat --release --example git`
