Function finalize_session_directory 

pub fn finalize_session_directory(
    sess: &Session,
    incr_comp_session: Option<IncrCompSession>,
    svh: Option<Svh>,
)

This function finalizes and thus ‘publishes’ the session directory by renaming it to s-{timestamp}-{svh} and releasing the file lock. This must not be called if there have been any compilation errors.