Function push 

pub fn push(path: &mut String, extra: &str)

Push a path component on an existing path. Only works if extra is a relative path.

use pijul_core::path::push;
let mut s = "a".to_string();
push(&mut s, "b");
assert_eq!(s, "a/b");
push(&mut s, "c");
assert_eq!(s, "a/b/c");