Pretty Print XML in Rust

Cargo.toml

[package]
name = "xmlformat"
version = "0.1.0"
authors = ["aaron"]
edition = "2018"

# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html

[dependencies]
xmltree = "0.10"
clap = "2.33"

main.rs

use std::fs::File;
use std::io::{Read, Write};
use xmltree::{Element, EmitterConfig};

use clap::{App, Arg};

fn main() {
    let matches = App::new("XML Format")
        .args(&[
            Arg::with_name("input")
                .required(true)
                .index(1)
                .help("the input file to use"),
            Arg::with_name("output")
                .short("o")
                .required(true)
                .takes_value(true)
                .help("the output file to use"),
        ])
        .get_matches();

    let out_path = matches.value_of("output").unwrap(); // unwrap OK because required arg
    let in_path = matches.value_of("input").unwrap(); // unwrap OK because required arg

    let mut in_file = File::open(in_path).expect("openinfile");
    let mut in_contents = String::new();
    in_file
        .read_to_string(&mut in_contents)
        .expect("readinfiletostring");
    drop(in_file);

    let el = Element::parse(in_contents.as_bytes()).expect("parsexml");
    let mut cfg = EmitterConfig::new();
    cfg.perform_indent = true;

    let mut out_file = File::create(out_path).expect("createoutfile");
    el.write_with_config(&mut out_file, cfg).expect("writexml");
    let _ = out_file.write("\n".as_bytes());
}

I simply wanted to leave a comment, that might be useful to some other people.
(as I came across your code while googling for several hours.)

Please feel free to disregard it if you're no longer using this code :)