use std::borrow::Cow;use std::{    io,    ops::{Deref, DerefMut},}; use bstr::BString;use git_transport::client::Capabilities; use crate::fetch::{Arguments, Response};use crate::handshake::Ref; /// Defines what to do next after certain [`Delegate`] operations.#[derive(PartialEq, Eq, Debug, Hash, Ord, PartialOrd, Clone, Copy)]pub enum Action {    /// Continue the typical flow of operations in this flow.    Continue,    /// Return at the next possible opportunity without making further requests, possibly after closing the connection.    Cancel,} /// The non-IO protocol delegate is the bare minimal interface needed to fully control the [`fetch`][crate::fetch()] operation, sparing/// the IO parts./// Async implementations must treat it as blocking and unblock it by evaluating it elsewhere.////// See [Delegate] for the complete trait.pub trait DelegateBlocking {    /// Return extra parameters to be provided during the handshake.    ///    /// Note that this method is only called once and the result is reused during subsequent handshakes which may happen    /// if there is an authentication failure.    fn handshake_extra_parameters(&self) -> Vec<(String, Option<String>)> {        Vec::new()    }    /// Called before invoking 'ls-refs' on the server to allow providing it with additional `arguments` and to enable `features`.    /// If the server `capabilities` don't match the requirements abort with an error to abort the entire fetch operation.    ///    /// Note that some arguments are preset based on typical use, and `features` are preset to maximize options.    /// The `server` capabilities can be used to see which additional capabilities the server supports as per the handshake which happened prior.    ///    /// If the delegate returns [`ls_refs::Action::Skip`], no 'ls-refs` command is sent to the server.    ///    /// Note that this is called only if we are using protocol version 2.    fn prepare_ls_refs(        &mut self,        _server: &Capabilities,        _arguments: &mut Vec<BString>,        _features: &mut Vec<(&str, Option<Cow<'_, str>>)>,    ) -> std::io::Result<ls_refs::Action> {        Ok(ls_refs::Action::Continue)    }     /// Called before invoking the 'fetch' interaction with `features` pre-filled for typical use    /// and to maximize capabilities to allow aborting an interaction early.    ///    /// `refs` is a list of known references on the remote based on the handshake or a prior call to ls_refs.    /// These can be used to abort early in case the refs are already known here.    ///    /// As there will be another call allowing to post arguments conveniently in the correct format, i.e. `want hex-oid`,    /// there is no way to set arguments at this time.    ///    /// `version` is the actually supported version as reported by the server, which is relevant in case the server requested a downgrade.    /// `server` capabilities is a list of features the server supports for your information, along with enabled `features` that the server knows about.    fn prepare_fetch(        &mut self,        _version: git_transport::Protocol,        _server: &Capabilities,        _features: &mut Vec<(&str, Option<Cow<'_, str>>)>,        _refs: &[Ref],    ) -> std::io::Result<Action> {        Ok(Action::Continue)    }     /// A method called repeatedly to negotiate the objects to receive in [`receive_pack(…)`][Delegate::receive_pack()].    ///    /// The first call has `previous_response` set to `None` as there was no previous response. Every call that follows `previous_response`    /// will be set to `Some`.    ///    /// ### If `previous_response` is `None`…    ///    /// Given a list of `arguments` to populate with wants, want-refs, shallows, filters and other contextual information to be    /// sent to the server. This method is called once.    /// Send the objects you `have` have afterwards based on the tips of your refs, in preparation to walk down their parents    /// with each call to `negotiate` to find the common base(s).    ///    /// Note that you should not `want` and object that you already have.    /// `refs` are the the tips of on the server side, effectively the latest objects _they_ have.    ///    /// Return `Action::Close` if you know that there are no `haves` on your end to allow the server to send all of its objects    /// as is the case during initial clones.    ///    /// ### If `previous_response` is `Some`…    ///    /// Populate `arguments` with the objects you `have` starting from the tips of _your_ refs, taking into consideration    /// the `previous_response` response of the server to see which objects they acknowledged to have. You have to maintain    /// enough state to be able to walk down from your tips on each call, if they are not in common, and keep setting `have`    /// for those which are in common if that helps teaching the server about our state and to acknowledge their existence on _their_ end.    /// This method is called until the other side signals they are ready to send a pack.    /// Return `Action::Close` if you want to give up before finding a common base. This can happen if the remote repository    /// has radically changed so there are no bases, or they are very far in the past, causing all objects to be sent.    fn negotiate(        &mut self,        refs: &[Ref],        arguments: &mut Arguments,        previous_response: Option<&Response>,    ) -> io::Result<Action>;} impl<T: DelegateBlocking> DelegateBlocking for Box<T> {    fn handshake_extra_parameters(&self) -> Vec<(String, Option<String>)> {        self.deref().handshake_extra_parameters()    }     fn prepare_ls_refs(        &mut self,        _server: &Capabilities,        _arguments: &mut Vec<BString>,        _features: &mut Vec<(&str, Option<Cow<'_, str>>)>,    ) -> io::Result<ls_refs::Action> {        self.deref_mut().prepare_ls_refs(_server, _arguments, _features)    }     fn prepare_fetch(        &mut self,        _version: git_transport::Protocol,        _server: &Capabilities,        _features: &mut Vec<(&str, Option<Cow<'_, str>>)>,        _refs: &[Ref],    ) -> io::Result<Action> {        self.deref_mut().prepare_fetch(_version, _server, _features, _refs)    }     fn negotiate(        &mut self,        refs: &[Ref],        arguments: &mut Arguments,        previous_response: Option<&Response>,    ) -> io::Result<Action> {        self.deref_mut().negotiate(refs, arguments, previous_response)    }} impl<T: DelegateBlocking> DelegateBlocking for &mut T {    fn handshake_extra_parameters(&self) -> Vec<(String, Option<String>)> {        self.deref().handshake_extra_parameters()    }     fn prepare_ls_refs(        &mut self,        _server: &Capabilities,        _arguments: &mut Vec<BString>,        _features: &mut Vec<(&str, Option<Cow<'_, str>>)>,    ) -> io::Result<ls_refs::Action> {        self.deref_mut().prepare_ls_refs(_server, _arguments, _features)    }     fn prepare_fetch(        &mut self,        _version: git_transport::Protocol,        _server: &Capabilities,        _features: &mut Vec<(&str, Option<Cow<'_, str>>)>,        _refs: &[Ref],    ) -> io::Result<Action> {        self.deref_mut().prepare_fetch(_version, _server, _features, _refs)    }     fn negotiate(        &mut self,        refs: &[Ref],        arguments: &mut Arguments,        previous_response: Option<&Response>,    ) -> io::Result<Action> {        self.deref_mut().negotiate(refs, arguments, previous_response)    }} #[cfg(feature = "blocking-client")]mod blocking_io {    use std::{        io::{self, BufRead},        ops::DerefMut,    };     use git_features::progress::Progress;     use crate::fetch::{DelegateBlocking, Response};    use crate::handshake::Ref;     /// The protocol delegate is the bare minimal interface needed to fully control the [`fetch`][crate::fetch()] operation.    ///    /// Implementations of this trait are controlled by code with intricate knowledge about how fetching works in protocol version V1 and V2,    /// so you don't have to.    /// Everything is tucked away behind type-safety so 'nothing can go wrong'©. Runtime assertions assure invalid    /// features or arguments don't make it to the server in the first place.    /// Please note that this trait mostly corresponds to what V2 would look like, even though V1 is supported as well.    pub trait Delegate: DelegateBlocking {        /// Receive a pack provided from the given `input`.        ///        /// Use `progress` to emit your own progress messages when decoding the pack.        ///        /// `refs` of the remote side are provided for convenience, along with the parsed `previous_response` response in case you want        /// to check additional acks.        fn receive_pack(            &mut self,            input: impl io::BufRead,            progress: impl Progress,            refs: &[Ref],            previous_response: &Response,        ) -> io::Result<()>;    }     impl<T: Delegate> Delegate for Box<T> {        fn receive_pack(            &mut self,            input: impl BufRead,            progress: impl Progress,            refs: &[Ref],            previous_response: &Response,        ) -> io::Result<()> {            self.deref_mut().receive_pack(input, progress, refs, previous_response)        }    }     impl<T: Delegate> Delegate for &mut T {        fn receive_pack(            &mut self,            input: impl BufRead,            progress: impl Progress,            refs: &[Ref],            previous_response: &Response,        ) -> io::Result<()> {            self.deref_mut().receive_pack(input, progress, refs, previous_response)        }    }}#[cfg(feature = "blocking-client")]pub use blocking_io::Delegate; #[cfg(feature = "async-client")]mod async_io {    use std::{io, ops::DerefMut};     use async_trait::async_trait;    use futures_io::AsyncBufRead;    use git_features::progress::Progress;     use crate::fetch::{DelegateBlocking, Response};    use crate::handshake::Ref;     /// The protocol delegate is the bare minimal interface needed to fully control the [`fetch`][crate::fetch()] operation.    ///    /// Implementations of this trait are controlled by code with intricate knowledge about how fetching works in protocol version V1 and V2,    /// so you don't have to.    /// Everything is tucked away behind type-safety so 'nothing can go wrong'©. Runtime assertions assure invalid    /// features or arguments don't make it to the server in the first place.    /// Please note that this trait mostly corresponds to what V2 would look like, even though V1 is supported as well.    #[async_trait(?Send)]    pub trait Delegate: DelegateBlocking {        /// Receive a pack provided from the given `input`, and the caller should consider it to be blocking as        /// most operations on the received pack are implemented in a blocking fashion.        ///        /// Use `progress` to emit your own progress messages when decoding the pack.        ///        /// `refs` of the remote side are provided for convenience, along with the parsed `previous_response` response in case you want        /// to check additional acks.        async fn receive_pack(            &mut self,            input: impl AsyncBufRead + Unpin + 'async_trait,            progress: impl Progress,            refs: &[Ref],            previous_response: &Response,        ) -> io::Result<()>;    }    #[async_trait(?Send)]    impl<T: Delegate> Delegate for Box<T> {        async fn receive_pack(            &mut self,            input: impl AsyncBufRead + Unpin + 'async_trait,            progress: impl Progress,            refs: &[Ref],            previous_response: &Response,        ) -> io::Result<()> {            self.deref_mut()                .receive_pack(input, progress, refs, previous_response)                .await        }    }     #[async_trait(?Send)]    impl<T: Delegate> Delegate for &mut T {        async fn receive_pack(            &mut self,            input: impl AsyncBufRead + Unpin + 'async_trait,            progress: impl Progress,            refs: &[Ref],            previous_response: &Response,        ) -> io::Result<()> {            self.deref_mut()                .receive_pack(input, progress, refs, previous_response)                .await        }    }}use crate::ls_refs;#[cfg(feature = "async-client")]pub use async_io::Delegate;