use std::path::PathBuf; use crate::store::{file, packed}; impl file::Store {    /// Return a packed transaction ready to receive updates. Use this to create or update `packed-refs`.    /// Note that if you already have a [`packed::Buffer`] then use its [`packed::Buffer::into_transaction()`] method instead.    pub(crate) fn packed_transaction(        &self,        lock_mode: git_lock::acquire::Fail,    ) -> Result<packed::Transaction, transaction::Error> {        let lock = git_lock::File::acquire_to_update_resource(self.packed_refs_path(), lock_mode, None)?;        Ok(match self.packed_buffer()? {            Some(packed) => packed::Transaction::new_from_pack_and_lock(packed, lock),            None => packed::Transaction::new_empty(lock),        })    }     /// Return a buffer for the packed file    pub fn packed_buffer(&self) -> Result<Option<packed::Buffer>, packed::buffer::open::Error> {        let need_more_than_these_bytes_to_use_mmap = 32 * 1024;        match packed::Buffer::open(self.packed_refs_path(), need_more_than_these_bytes_to_use_mmap) {            Ok(buf) => Ok(Some(buf)),            Err(packed::buffer::open::Error::Io(err)) if err.kind() == std::io::ErrorKind::NotFound => Ok(None),            Err(err) => Err(err),        }    }     /// Return the path at which packed-refs would usually be stored    pub fn packed_refs_path(&self) -> PathBuf {        self.base.join("packed-refs")    }} ///pub mod transaction {    use quick_error::quick_error;     use crate::store::packed;     quick_error! {        /// The error returned by [`file::Store::packed_transaction`][crate::file::Store::packed_transaction()].        #[derive(Debug)]        #[allow(missing_docs)]        pub enum Error {            BufferOpen(err: packed::buffer::open::Error) {                display("An existing pack couldn't be opened or read when preparing a transaction")                source(err)                from()            }            TransactionLock(err: git_lock::acquire::Error) {                display("The lock for a packed transaction could not be obtained")                source(err)                from()            }        }    }}