use git_features::hash; use crate::{write, File, Version}; impl File {    /// Write the index to `out` with `options`, to be readable by [`File::at()`], returning the version that was actually written    /// to retain all information of this index.    pub fn write_to(&self, mut out: impl std::io::Write, options: write::Options) -> std::io::Result<Version> {        let mut hasher = hash::Write::new(&mut out, options.hash_kind);        let version = self.state.write_to(&mut hasher, options)?;         let hash = hasher.hash.digest();        out.write_all(&hash)?;        Ok(version)    }}