lint: enable clippy restriction lints, disable redundant dylint rule

Enable `clippy::clone_on_ref_ptr`, `clippy::if_then_some_else_none`, and
`clippy::unnecessary_lazy_evaluations` as warnings, which the existing
`cargo clippy -- -D warnings` invocation in `test.sh` promotes to hard
errors in CI. Disable `perfectionist::arc_rc_clone` in `dylint.toml`
because `clippy::clone_on_ref_ptr` now covers the same ground in the
default lint pass.

Apply the single resulting code fix in `App::run`, replacing an
`if`/`else` that produced `Some(1)`/`None` with `.then(|| ...)`.

Author: claude

Cargo.toml

@@ -91,6 +91,11 @@ zero-copy-pads = "0.2.0"
 [lints.rust]
 unexpected_cfgs = { level = "warn", check-cfg = ['cfg(dylint_lib, values("perfectionist"))'] }
 
+[lints.clippy]
+clone_on_ref_ptr = "warn"
+if_then_some_else_none = "warn"
+unnecessary_lazy_evaluations = "warn"
+
 [dev-dependencies]
 build-fs-tree = "0.8.1"
 command-extra = "1.0.0"

dylint.toml

@@ -3,6 +3,11 @@ libraries = [
     { git = "https://github.com/KSXGitHub/perfectionist", tag = "0.0.0-rc.14" },
 ]
 
+[perfectionist]
+disable = [
+    { name = "arc_rc_clone", reason = "`arc_rc_clone` is enforced by `clippy::clone_on_ref_ptr` instead" },
+]
+
 ["perfectionist::derive_ordering"]
 style = "prefix_then_alphabetical"
 prefix = [

src/app.rs

@@ -144,13 +144,11 @@ impl App {
         let threads = match self.args.threads {
             Threads::Auto => {
                 let disks = Disks::new_with_refreshed_list();
-                if any_path_is_in_hdd::<Disk, hdd::RealFs>(&self.args.files, &disks) {
+                any_path_is_in_hdd::<Disk, hdd::RealFs>(&self.args.files, &disks).then(|| {
                     eprintln!("warning: HDD detected, the thread limit will be set to 1");
                     eprintln!("hint: You can pass --threads=max disable this behavior");
-                    Some(1)
-                } else {
-                    None
-                }
+                    1
+                })
             }
             Threads::Max => None,
             Threads::Fixed(threads) => Some(threads.get()),