node/worker/garbage: Clean up

Clippy reports dead code on all variants except `Hours` on `Expiry`,
since the type is defined in a binary crate.

Allow dead code here, just in case we want to use the other variants in
the future. They are not a maintenance burden, as the implementation is
simple and does not see much change.

Slightly refactor:
 - `impl std::fmt::Display for Expiry` to look cleaner.
 - `fn collect` to borrow `RepoId`, since it only needs
   a borrow, and a a borrow of `Expiry` to spare a copy
   at the only call site.
 - The constant for the default value of `Expiry` to be
   associated with the type `Expiry`.

Remove a remark about the default value of `Expiry` from `FetchConfig`,
as the default value is not a concern there, but rather wherever
`Expiry` is initialized.

crates/radicle-node/src/worker.rs

@@ -61,8 +61,7 @@ pub struct TaskResult {
 pub struct FetchConfig {
     /// Public key of the local peer.
     pub local: crypto::PublicKey,
-    /// Configuration for `git gc` garbage collection. Defaults to `1
-    /// hour ago`.
+    /// Configuration for `git gc` garbage collection.
     pub expiry: garbage::Expiry,
 }
 
@@ -267,7 +266,7 @@ impl Worker {
             refs_at,
         )?;
 
-        if let Err(e) = garbage::collect(&self.storage, rid, *expiry) {
+        if let Err(e) = garbage::collect(&self.storage, &rid, expiry) {
             // N.b. ensure that `git gc` works in debug mode.
             debug_assert!(false, "`git gc` failed: {e}");
 

crates/radicle-node/src/worker/garbage.rs

@@ -4,40 +4,53 @@ use std::{fmt, io};
 use radicle::prelude::RepoId;
 use radicle::storage::ReadStorage;
 
-/// Default expiry time for objects.
-pub const EXPIRY_DEFAULT: Expiry = Expiry::Hours(1);
-
 /// Expiry of objects for garbage collector.
 #[derive(Copy, Clone, Debug, PartialEq, Eq)]
 pub enum Expiry {
+    #[allow(dead_code)]
     Now,
+    #[allow(dead_code)]
     Seconds(usize),
     Hours(usize),
+    #[allow(dead_code)]
     Days(usize),
+    #[allow(dead_code)]
     Weeks(usize),
 }
 
+impl Expiry {
+    const DEFAULT: Self = Expiry::Hours(1);
+}
+
 impl Default for Expiry {
     fn default() -> Self {
-        EXPIRY_DEFAULT
+        Self::DEFAULT
     }
 }
 
 impl fmt::Display for Expiry {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-        match self {
-            Self::Now => f.write_str("now"),
-            Self::Seconds(s) => write!(f, "{s}.seconds.ago"),
-            Self::Hours(s) => write!(f, "{s}.hours.ago"),
-            Self::Days(s) => write!(f, "{s}.days.ago"),
-            Self::Weeks(s) => write!(f, "{s}.weeks.ago"),
-        }
+        #[rustfmt::skip]
+        let (quantity, unit) = match self {
+            Self::Now => return f.write_str("now"),
+
+            Self::Seconds(quantity) => (quantity, "seconds"),
+            Self::Hours  (quantity) => (quantity, "hours"  ),
+            Self::Days   (quantity) => (quantity, "days"   ),
+            Self::Weeks  (quantity) => (quantity, "weeks"  ),
+        };
+
+        write!(f, "{quantity}.{unit}.ago")
     }
 }
 
 /// Run Git garbage collector.
-pub fn collect(storage: &impl ReadStorage, rid: RepoId, expiry: Expiry) -> io::Result<ExitStatus> {
-    let git_dir = storage.path_of(&rid);
+pub fn collect(
+    storage: &impl ReadStorage,
+    rid: &RepoId,
+    expiry: &Expiry,
+) -> io::Result<ExitStatus> {
+    let git_dir = storage.path_of(rid);
     let mut gc = Command::new("git");
     gc.current_dir(git_dir)
         .env_clear()