Function lexically_normal 

pub fn lexically_normal(path: &Path) -> PathBuf

Resolves . and .. without touching the filesystem.

commondir holds a relative path such as ../.., and leaving it in place would make every message name a path no user recognises. export-key needs the same thing for a destination that does not exist yet, which is why this is public: a path it cannot resolve is a path it cannot prove lies outside the repository.

Only safe on a path whose components are known not to be symlinks — popping on .. is what a symlink would make wrong.