Function write_entry 

fn write_entry(
    writer: &mut impl Write,
    path: &Path,
    stat: &Stat,
    ifmt: FileType,
    size: u64,
    nlink: usize,
    rdev: u64,
    payload: impl AsRef<OsStr>,
    content: &[u8],
    digest: Option<&str>,
) -> Result