lints: adopt canonical lints; fix usize underflow panic on dir_length(0)

[h4x0r]

What

shrinkpath carried no [lints] block at all. This adds the canonical recipe and fixes everything it lit up.

The bug the missing lint was hiding

ShrinkOptions::dir_length(n) is a public builder setter that accepts any usize. abbreviate_segment then takes len characters by pushing the first and taking len - 1 more — so dir_length(0) underflows:

thread '...' panicked at src/strategy/fish.rs:27:25:
attempt to subtract with overflow

Reachable from ordinary safe caller code — no unsafe, no malformed input, just a value the builder advertises as legal. In a release build overflow checks are off, so 0 - 1 becomes usize::MAX and take() yields the whole segment: no panic, but the segment comes back completely unabbreviated, which is the opposite of what dir_length(0) asks for.

Fixed with len.saturating_sub(1), so the leading character survives — mirroring the dot branch, which already yields "." at len == 0.

Commits

• RED — test(fish): prove dir_length(0) panics with usize underflow (two tests: one on the internal helper, one through the public shrink()/ShrinkOptions API)
• GREEN — fix(fish): saturate dir_length(0); adopt canonical lints

Unwraps removed structurally

Site	Was	Now
strategy/fish.rs	chars.next().unwrap()	let-else returning ""
path_info.rs	parts.last().unwrap() + parts[..len-1]	split_last() — also retires the separate is_empty() guard and the len - 1 index
fs_aware.rs	chars.next().unwrap()	map_or_else, folding the is_empty() special case into the same expression

What lit up, and how each was closed

Lint	Sites	Disposition
clippy::unwrap_used	3	Fixed (table above)
clippy::return_self_not_must_use	7	Fixed — #[must_use] on the builder methods
clippy::redundant_closure	5	Fixed
clippy::doc_markdown	2	Fixed
clippy::single_char_pattern	2	Fixed
clippy::map_unwrap_or	1	Fixed (is_ok_and)
clippy::format_push_string	1	Fixed (write! + fmt::Write)

No lint was added to an allow list to make this pass. The unit tests inside src carry the sanctioned #![cfg_attr(test, allow(clippy::unwrap_used, clippy::expect_used))].

One thing to decide

The [lints] table is honored by Cargo 1.74+; this crate declares rust-version = "1.70". Older cargo ignores the table with a warning rather than failing, and CI runs a modern toolchain, so enforcement is real where it is checked. I left rust-version alone rather than raise a published library's MSRV as a side effect of a lints PR — flagging it as a separate call.

Gate

cargo build --all-targets --all-features · cargo test --all-features (88 tests) · cargo clippy --all-targets --all-features -- -D warnings · cargo fmt --check — all clean.

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