Function normalize 

pub fn normalize<'a>(
    path: Cow<'a, Path>,
    current_dir: &Path,
) -> Option<Cow<'a, Path>>

Resolve relative components virtually, eliminating intermediate .. without accessing the filesystem.

For example, this turns a/./b/c/.././.. into a, and turns /a/../b/.. into /.

for (input, expected) in [
    ("a/./b/c/.././..", "a"),
    ("/a/../b/..", "/"),
    ("/base/a/..", "/base"),
    ("./a/..", "."),
    ("./a/../..", "/"),
    (".///", ".///"),
    ("a//b", "a//b"),
    ("/base/../base", "/base"),
] {
    let input = Path::new(input);
    let expected = Path::new(expected);
    assert_eq!(normalize(input.into(), Path::new("/cwd")), Some(expected.into()));
}

Leading . components as well as duplicate separators are left untouched.

This is particularly useful when manipulating paths that are based on user input, and not resolving intermediate symlinks keeps the path similar to what the user provided. If that’s not desirable, use realpath() instead.

Note that we will use the current_dir if we run out of path components to pop off, which is expected to be absolute as typical return value of std::env::current_dir() or gix_fs::current_dir(…) when core.precomposeUnicode is known. As a current_dir like /c can be exhausted by paths like ../../r, None will be returned to indicate the inability to produce a logically consistent path.