breadshot: expand ~ in save_dir, align Cargo.toml version with tag

- config.rs: expand a leading ~ in the save_dir config value on load.
  The documented example config (save_dir = "~/Pictures/Screenshots")
  was previously taken literally, silently creating ./~/Pictures/... in
  the current working directory. Added unit tests.
- Cargo.toml: 1.0.0 -> 0.1.0, matching the only existing tag (v0.1.0).
  breadshot --version previously reported nine releases ahead of the
  actual release history.

src/config.rs

@@ -38,8 +38,10 @@ impl Config {
         }
         let content = std::fs::read_to_string(path)
             .with_context(|| format!("reading {}", path.display()))?;
-        toml::from_str(&content)
-            .with_context(|| format!("parsing {}", path.display()))
+        let mut config: Self = toml::from_str(&content)
+            .with_context(|| format!("parsing {}", path.display()))?;
+        config.save_dir = expand_tilde(config.save_dir);
+        Ok(config)
     }
 }
 
@@ -49,3 +51,56 @@ pub fn default_path() -> PathBuf {
         .join("breadshot")
         .join("config.toml")
 }
+
+/// Expand a leading `~` (or `~/...`) to the user's home directory, the way a
+/// shell would. `PathBuf`'s `Deserialize` does no such expansion, so a
+/// documented config value like `save_dir = "~/Pictures/Screenshots"` would
+/// otherwise be taken literally and create a `./~/Pictures/Screenshots`
+/// directory relative to the current working directory.
+fn expand_tilde(path: PathBuf) -> PathBuf {
+    let Some(s) = path.to_str() else {
+        return path;
+    };
+    if s == "~" {
+        return dirs::home_dir().unwrap_or(path);
+    }
+    if let Some(rest) = s.strip_prefix("~/") {
+        if let Some(home) = dirs::home_dir() {
+            return home.join(rest);
+        }
+    }
+    path
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn expand_tilde_prefix() {
+        let home = dirs::home_dir().unwrap();
+        assert_eq!(
+            expand_tilde(PathBuf::from("~/Pictures/Screenshots")),
+            home.join("Pictures/Screenshots")
+        );
+    }
+
+    #[test]
+    fn expand_tilde_bare() {
+        let home = dirs::home_dir().unwrap();
+        assert_eq!(expand_tilde(PathBuf::from("~")), home);
+    }
+
+    #[test]
+    fn expand_tilde_absolute_untouched() {
+        let p = PathBuf::from("/var/tmp/shots");
+        assert_eq!(expand_tilde(p.clone()), p);
+    }
+
+    #[test]
+    fn expand_tilde_no_expansion_mid_path() {
+        // Only a leading ~ is special, matching shell behavior.
+        let p = PathBuf::from("/home/user/~weird");
+        assert_eq!(expand_tilde(p.clone()), p);
+    }
+}