Function broot::path::path_from

pub fn path_from<P: AsRef<Path>>(
    base_dir: P, 
    anchor: PathAnchor, 
    input: &str
) -> PathBuf

build a usable path from a user input which may be absolute (if it starts with / or ~) or relative to the supplied base_dir. (we might want to try detect windows drives in the future, too)