Function melib::backends::maildir::backend::add_path_to_index

fn add_path_to_index(
    hash_index: &HashIndexes, 
    mailbox_hash: MailboxHash, 
    path: &Path, 
    cache_dir: &BaseDirectories, 
    file_name: PathBuf, 
    buf: &mut Vec<u8>
) -> Result<Envelope>