feat: add git daemon server and cli command

[aymanbagabas]

This adds a new gogit daemon command that starts a Git TCP server. It uses a local pure Go implementation for handling Git protocol server requests using the standard library net package under server/git.

// Handler is the interface that handles TCP requests for the Git protocol.
type Handler interface {
	// ServeTCP handles a TCP connection for the Git protocol.
	ServeTCP(ctx context.Context, c io.ReadWriteCloser, req *packp.GitProtoRequest)
}

// HandlerFunc is a function that implements the Handler interface.
type HandlerFunc func(ctx context.Context, c io.ReadWriteCloser, req *packp.GitProtoRequest)

// ServeTCP implements the Handler interface.
func (f HandlerFunc) ServeTCP(ctx context.Context, c io.ReadWriteCloser, req *packp.GitProtoRequest)

// Server is a TCP server that handles Git protocol requests.
type Server struct {
	// Addr is the address to listen on. If empty, it defaults to ":9418".
	Addr string

	// Handler is the handler for Git protocol requests. It uses
	// [DefaultHandler] when nil.
	Handler Handler

	// ErrorLog is the logger used to log errors. When nil, it won't log
	// errors.
	ErrorLog *log.Logger

	// BaseContext optionally specifies a function to create a base context for
	// the server listeners. If nil, [context.Background] will be used.
	// The provided listener is the specific listener that is about to start
	// accepting connections.
	BaseContext func(net.Listener) context.Context

	// ConnContext optionally specifies a function to create a context for each
	// connection. If nil, the context will be derived from the server's base
	// context.
	ConnContext func(context.Context, net.Conn) context.Context
}

func (s *Server) Close() error
func (s *Server) ListenAndServe() error
func (s *Server) Serve(ln net.Listener) error
func (s *Server) Shutdown(ctx context.Context) error

[Copilot]

Pull Request Overview

This PR introduces a pure Go Git daemon server implementation under server/git and a new gogit daemon CLI command.

• Adds Server type with lifecycle methods (ListenAndServe, Shutdown, etc.) for Git TCP protocol handling.
• Introduces LoggingMiddleware to wrap protocol handlers with request logging.
• Extends the CLI with a daemon subcommand to launch the Git daemon and improves root command error handling.

Reviewed Changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 3 comments.

File	Description
server/git/server.go	Core TCP server implementation for Git protocol.
server/git/logging.go	Middleware to log incoming Git requests.
cmd/gogit/main.go	Enhanced root command error reporting for remote errors.
cmd/gogit/daemon.go	New daemon command to start the Git daemon.

Comments suppressed due to low confidence (2)

server/git/server.go:54

• The doc for Handler refers to [DefaultHandler] but the actual fallback is DefaultBackend. Update the reference to [DefaultBackend] to match implementation.

	// [DefaultHandler] when nil.

server/git/server.go:85

• [nitpick] There are no tests validating shutdown behavior (idle connection polling, listener closure, context cancellation). Consider adding unit tests for Shutdown to ensure graceful teardown works as expected.

func (s *Server) Shutdown(ctx context.Context) error {

[Copilot]

[nitpick] The --export-all flag is registered but never used. Consider wiring it into the gitbackend.NewBackend loader logic or removing the flag.

[pjbgf]

@aymanbagabas thanks for working on this. Overall LGTM, apart from the stat/lstat below.