use std::{    cell::{BorrowError, BorrowMutError},    time::SystemTime,}; use git_ref::file; use crate::easy; #[derive(Debug, thiserror::Error)]pub enum Error {    #[error(transparent)]    PackedRefsOpen(#[from] git_ref::packed::buffer::open::Error),    #[error("BUG: Part of interior state could not be borrowed.")]    BorrowState(#[from] easy::borrow::state::Error),} impl From<std::cell::BorrowError> for Error {    fn from(err: BorrowError) -> Self {        Error::BorrowState(easy::borrow::state::Error::Borrow(err))    }} impl From<std::cell::BorrowMutError> for Error {    fn from(err: BorrowMutError) -> Self {        Error::BorrowState(easy::borrow::state::Error::BorrowMut(err))    }} #[derive(Default)]pub(crate) struct ModifieablePackedRefsBuffer {    pub(crate) buffer: Option<git_ref::packed::Buffer>,    modified: Option<SystemTime>,} impl ModifieablePackedRefsBuffer {    pub fn assure_packed_refs_uptodate(        &mut self,        file: &file::Store,    ) -> Result<(), git_ref::packed::buffer::open::Error> {        let packed_refs_modified_time = || file.packed_refs_path().metadata().and_then(|m| m.modified()).ok();        if self.buffer.is_none() {            self.buffer = file.packed_buffer()?;            if self.buffer.is_some() {                self.modified = packed_refs_modified_time();            }        } else {            let recent_modification = packed_refs_modified_time();            match (&self.modified, recent_modification) {                (None, None) => {}                (Some(_), None) => {                    self.buffer = None;                    self.modified = None                }                (Some(cached_time), Some(modified_time)) => {                    if *cached_time < modified_time {                        self.buffer = file.packed_buffer()?;                        self.modified = Some(modified_time);                    }                }                (None, Some(modified_time)) => {                    self.buffer = file.packed_buffer()?;                    self.modified = Some(modified_time);                }            }        }        Ok(())    }}