Add test for the behaviour of `fs::copy` when `to` is a symlink
Add test for the behaviour of `fs::copy` when `to` is a symlink

aidancully/rust,aidancully/rust,graydon/rust,graydon/rust,graydon/rust,graydon/rust,graydon/rust,aidancully/rust,aidancully/rust,graydon/rust,aidancully/rust,aidancully/rust