stty: fix: reject "+hex" in parse_saved_state

[Rudxain]

Fixes this pitfall: rust-lang/rust-clippy#16213

Related: #9255

[github-actions]

GNU testsuite comparison:

Skipping an intermittent issue tests/tail/overlay-headers (passes in this run but fails in the 'main' branch)

[sylvestre]

@Rudxain still draft after 2 weeks, are you going to work on it? thanks

[Rudxain]

are you going to work on it? thanks

Yes! This PR can be merged as-is, but I want to replace from_str_radix by some internal utility. I could simply write an ad-hoc hex-parser, but I assume there's already one, so it's better to reuse the code. The closest I could find was this:

coreutils/src/uucore/src/lib/features/parser/num_parser.rs

Lines 39 to 54 in e6467b1

	/// Return the digit value of a character in the given base
	fn digit(&self, c: char) -> Option<u64> {
	fn from_decimal(c: char) -> u64 {
	u64::from(c) - u64::from('0')
	}
	match self {
	Self::Binary => ('0'..='1').contains(&c).then(|| from_decimal(c)),
	Self::Octal => ('0'..='7').contains(&c).then(|| from_decimal(c)),
	Self::Decimal => c.is_ascii_digit().then(|| from_decimal(c)),
	Self::Hexadecimal => match c.to_ascii_lowercase() {
	'0'..='9' => Some(from_decimal(c)),
	c @ 'a'..='f' => Some(u64::from(c) - u64::from('a') + 10),
	_ => None,
	},
	}
	}

Should I use that? Or is there something more appropriate?

[Rudxain]

I didn't expect the workflow queue to be cancelled 😕

[sylvestre]

Restarted

[Rudxain]

BTW, this branch is soft-blocked on this PR. Should I include that patch into this PR, or should I keep it separate for better scoping?

[github-actions]

GNU testsuite comparison:

Skipping an intermittent issue tests/tail/inotify-dir-recreate (passes in this run but fails in the 'main' branch)