Rename files with Rust

Cargo.toml

[package]
name = "jslife"
version = "0.1.0"
authors = ["Do Duy"]

[dependencies]
walkdir = "2.0"

main.rs

extern crate walkdir;

use walkdir::WalkDir;

fn rename() -> std::io::Result<()> {
    for entry in WalkDir::new(".") {
        let path = entry?.path().to_owned();
        let ex = path.extension();
        if path.is_file() && ex.is_some() && ex.unwrap() == "lif" {
            let mut new_path = path.clone();
            new_path.set_extension("rle");
            std::fs::copy(&path, &new_path)?;
            std::fs::remove_file(&path);
        }
    }

    Ok(())
}

fn main() {
    rename();
}