From d67e7d071d332d746382dfa602ea474b0ca2e865 Mon Sep 17 00:00:00 2001
From: tjh <x@tjh.dev>
Date: Wed, 21 May 2025 23:45:37 +0100
Subject: [PATCH] knotserver: git: add support for git protocol v2

v1-style requests are unaffected and v0 (dumb-protocol) requests remain
unsupported.
---
 knotserver/git.go                 | 12 +++++-----
 knotserver/git/service/service.go | 37 +++++++++++++++++++------------
 2 files changed, 30 insertions(+), 19 deletions(-)

diff --git a/knotserver/git.go b/knotserver/git.go
index 1a5d430d..82c1c522 100644
--- a/knotserver/git.go
+++ b/knotserver/git.go
@@ -31,8 +31,9 @@ func (d *Handle) InfoRefs(w http.ResponseWriter, r *http.Request) {
 	}
 
 	cmd := service.ServiceCommand{
-		Dir:    repoPath,
-		Stdout: w,
+		GitProtocol: r.Header.Get("Git-Protocol"),
+		Dir:         repoPath,
+		Stdout:      w,
 	}
 
 	serviceName := r.URL.Query().Get("service")
@@ -81,9 +82,10 @@ func (d *Handle) UploadPack(w http.ResponseWriter, r *http.Request) {
 	d.l.Info("git: executing git-upload-pack", "handler", "UploadPack", "repo", repo)
 
 	cmd := service.ServiceCommand{
-		Dir:    repo,
-		Stdout: w,
-		Stdin:  bodyReader,
+		GitProtocol: r.Header.Get("Git-Protocol"),
+		Dir:         repo,
+		Stdout:      w,
+		Stdin:       bodyReader,
 	}
 
 	w.WriteHeader(http.StatusOK)
diff --git a/knotserver/git/service/service.go b/knotserver/git/service/service.go
index 04051c8b..e6fadda1 100644
--- a/knotserver/git/service/service.go
+++ b/knotserver/git/service/service.go
@@ -15,19 +15,20 @@ import (
 // Mostly from charmbracelet/soft-serve and sosedoff/gitkit.
 
 type ServiceCommand struct {
-	Dir    string
-	Stdin  io.Reader
-	Stdout http.ResponseWriter
+	GitProtocol string
+	Dir         string
+	Stdin       io.Reader
+	Stdout      http.ResponseWriter
 }
 
 func (c *ServiceCommand) InfoRefs() error {
 	cmd := exec.Command("git", []string{
 		"upload-pack",
 		"--stateless-rpc",
-		"--advertise-refs",
+		"--http-backend-info-refs",
 		".",
 	}...)
-
+	cmd.Env = append(cmd.Env, fmt.Sprintf("GIT_PROTOCOL=%s", c.GitProtocol))
 	cmd.Dir = c.Dir
 	cmd.SysProcAttr = &syscall.SysProcAttr{Setpgid: true}
 	stdoutPipe, _ := cmd.StdoutPipe()
@@ -38,14 +39,16 @@ func (c *ServiceCommand) InfoRefs() error {
 		return err
 	}
 
-	if err := packLine(c.Stdout, "# service=git-upload-pack\n"); err != nil {
-		log.Printf("git: failed to write pack line: %s", err)
-		return err
-	}
+	if !strings.Contains(c.GitProtocol, "version=2") {
+		if err := packLine(c.Stdout, "# service=git-upload-pack\n"); err != nil {
+			log.Printf("git: failed to write pack line: %s", err)
+			return err
+		}
 
-	if err := packFlush(c.Stdout); err != nil {
-		log.Printf("git: failed to flush pack: %s", err)
-		return err
+		if err := packFlush(c.Stdout); err != nil {
+			log.Printf("git: failed to flush pack: %s", err)
+			return err
+		}
 	}
 
 	buf := bytes.Buffer{}
@@ -71,10 +74,16 @@ func (c *ServiceCommand) InfoRefs() error {
 func (c *ServiceCommand) UploadPack() error {
 	var stderr bytes.Buffer
 
-	cmd := exec.Command("git", "-c", "uploadpack.allowFilter=true",
-		"upload-pack", "--stateless-rpc", ".")
+	cmd := exec.Command("git", []string{
+		"-c", "uploadpack.allowFilter=true",
+		"upload-pack",
+		"--stateless-rpc",
+		".",
+	}...)
+
 	cmd.Dir = c.Dir
 	cmd.SysProcAttr = &syscall.SysProcAttr{Setpgid: true}
+	cmd.Env = append(cmd.Env, fmt.Sprintf("GIT_PROTOCOL=%s", c.GitProtocol))
 
 	stdoutPipe, err := cmd.StdoutPipe()
 	if err != nil {
-- 
2.51.2