copy: Updated.

copy/Cargo.toml

@@ -2,5 +2,6 @@
 name = "copy"
 version = "0.1.0"
 authors = ["You <you@example.com>"]
+edition = "2018"
 
 [dependencies]

copy/src/main.rs

@@ -1,3 +1,6 @@
+#![warn(rust_2018_idioms)]
+#![allow(elided_lifetimes_in_paths)]
+
 use std::fs;
 use std::io;
 use std::path::Path;