Fix clippy/compile warnings

Presumably these came with the new version of the rust compiler that
was recently released. The compile warning fix suggested by the
compiler/clippy was incorrect as the field in the `Response::Real`
variant is (kinda) used. Adding a name to the match clause seems
to kill the warning. The remaining fixes are exactly what clippy
suggested.

src/network.rs

@@ -36,7 +36,7 @@ enum Response<'a> {
 impl Response<'_> {
     fn has_header(&self, name: &str) -> bool {
         match self {
-            Response::Real(response, _) => response.headers().contains_key(name),
+            Response::Real(response, _permit) => response.headers().contains_key(name),
             #[cfg(test)]
             Response::Mock(_) => false,
         }

src/serialization.rs

@@ -518,7 +518,7 @@ pub mod spanned {
     thread_local! {
         /// Hack to work around `toml::Spanned` failing to be deserialized when
         /// used with the `toml::Value` deserializer.
-        pub(super) static DISABLE_SPANNED_DESERIALIZATION: Cell<bool> = Cell::new(false);
+        pub(super) static DISABLE_SPANNED_DESERIALIZATION: Cell<bool> = const { Cell::new(false) };
     }
 
     /// A spanned value, indicating the range at which it is defined in the source.

src/storage.rs

@@ -2828,6 +2828,7 @@ fn create_unpack_lock(unpack_dir: &Path) -> Result<(), io::Error> {
     // which may have been extracted from the package.
     let mut ok = OpenOptions::new()
         .create(true)
+        .truncate(true)
         .read(true)
         .write(true)
         .open(lockfile)?;