Try to get rid of owned types

Inspired by https://www.youtube.com/watch?v=A4cKi7PTJSs. This turns a
lot of cloning Strings and PathBufs into Rcs.

src/storage.rs

@@ -1,49 +1,46 @@
 use std::error::Error;
 use std::fs::read_dir;
-use std::path::PathBuf;
+use std::path::Path;
+use std::rc::Rc;
 use std::str::FromStr;
 use std::time::{SystemTime, UNIX_EPOCH};
 
 pub trait Storage {
-  fn write_filename(&self) -> PathBuf;
-  fn read_filename(&self) -> Result<PathBuf, Box<dyn Error>>;
+  fn write_filename(&self) -> Box<Path>;
+  fn read_filename(&self) -> Result<Box<Path>, Box<dyn Error>>;
   fn recent_date(&self) -> Result<u64, Box<dyn Error>>;
 }
 
 #[derive(Debug, Clone)]
-pub struct SimpleStorage(PathBuf);
+pub struct SimpleStorage(Rc<Path>);
 
 impl SimpleStorage {
   #[must_use]
-  pub const fn new(base: PathBuf) -> Self {
+  pub const fn new(base: Rc<Path>) -> Self {
     Self(base)
   }
 
-  fn get_path(&self, date: Option<u64>) -> PathBuf {
-    match date {
-      Some(d) => self.0.join(d.to_string()),
-      None => self.0.clone(),
-    }
+  fn get_path(&self, date: u64) -> Box<Path> {
+    self.0.join(date.to_string()).into()
   }
 }
 
 impl Storage for SimpleStorage {
-  fn write_filename(&self) -> PathBuf {
-    self.get_path(Some(
+  fn write_filename(&self) -> Box<Path> {
+    self.get_path(
       SystemTime::now()
         .duration_since(UNIX_EPOCH)
         .unwrap()
         .as_secs(),
-    ))
+    )
   }
 
-  fn read_filename(&self) -> Result<PathBuf, Box<dyn Error>> {
-    Ok(self.get_path(Some(self.recent_date()?)))
+  fn read_filename(&self) -> Result<Box<Path>, Box<dyn Error>> {
+    Ok(self.get_path(self.recent_date()?))
   }
 
   fn recent_date(&self) -> Result<u64, Box<dyn Error>> {
-    let dir = self.get_path(None);
-    read_dir(dir)?
+    read_dir(&self.0)?
       .map(|entry| {
         entry
           .ok()