Function figment::util::diff_paths

pub fn diff_paths<P, B>(path: P, base: B) -> Option<PathBuf> where
    P: AsRef<Path>,
    B: AsRef<Path>, 

A helper function to determine the relative path to path from base.

Returns None if there is no relative path from base to path, that is, base and path do not share a common ancestor. path and base must be either both absolute or both relative; returns None if one is relative and the other absolute.

use std::path::Path;
use figment::util::diff_paths;

// Paths must be both relative or both absolute.
assert_eq!(diff_paths("/a/b/c", "b/c"), None);
assert_eq!(diff_paths("a/b/c", "/b/c"), None);

// The root/relative root is always a common ancestor.
assert_eq!(diff_paths("/a/b/c", "/b/c"), Some("../../a/b/c".into()));
assert_eq!(diff_paths("c/a", "b/c/a"), Some("../../../c/a".into()));

let bar = "/foo/bar";
let baz = "/foo/bar/baz";
let quux = "/foo/bar/quux";

assert_eq!(diff_paths(bar, baz), Some("../".into()));
assert_eq!(diff_paths(baz, bar), Some("baz".into()));
assert_eq!(diff_paths(quux, baz), Some("../quux".into()));
assert_eq!(diff_paths(baz, quux), Some("../baz".into()));
assert_eq!(diff_paths(bar, quux), Some("../".into()));
assert_eq!(diff_paths(baz, bar), Some("baz".into()));