git: use system's git upload-pack

This is an intermediate workaround for
https://github.com/go-git/go-git/issues/1062. This should also fix #33.

2 files changed, 146 insertions, 0 deletions

diff --git a/git/service/service.go b/git/service/service.go
new file mode 100644
index 0000000..d2c7fdd
--- /dev/null
+++ b/git/service/service.go
@@ -0,0 +1,121 @@
+package service
+
+import (
+	"bytes"
+	"fmt"
+	"io"
+	"log"
+	"net/http"
+	"os/exec"
+	"strings"
+	"syscall"
+)
+
+// Mostly from charmbracelet/soft-serve and sosedoff/gitkit.
+
+type ServiceCommand struct {
+	Dir    string
+	Stdin  io.Reader
+	Stdout http.ResponseWriter
+}
+
+func (c *ServiceCommand) InfoRefs() error {
+	cmd := exec.Command("git", []string{
+		"upload-pack",
+		"--stateless-rpc",
+		"--advertise-refs",
+		".",
+	}...)
+
+	cmd.Dir = c.Dir
+	cmd.SysProcAttr = &syscall.SysProcAttr{Setpgid: true}
+	stdoutPipe, _ := cmd.StdoutPipe()
+	cmd.Stderr = cmd.Stdout
+
+	if err := cmd.Start(); err != nil {
+		log.Printf("git: failed to start git-upload-pack (info/refs): %s", err)
+		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 err := packFlush(c.Stdout); err != nil {
+		log.Printf("git: failed to flush pack: %s", err)
+		return err
+	}
+
+	buf := bytes.Buffer{}
+	if _, err := io.Copy(&buf, stdoutPipe); err != nil {
+		log.Printf("git: failed to copy stdout to tmp buffer: %s", err)
+		return err
+	}
+
+	if err := cmd.Wait(); err != nil {
+		out := strings.Builder{}
+		_, _ = io.Copy(&out, &buf)
+		log.Printf("git: failed to run git-upload-pack; err: %s; output: %s", err, out.String())
+		return err
+	}
+
+	if _, err := io.Copy(c.Stdout, &buf); err != nil {
+		log.Printf("git: failed to copy stdout: %s", err)
+	}
+
+	return nil
+}
+
+func (c *ServiceCommand) UploadPack() error {
+	cmd := exec.Command("git", []string{
+		"-c", "uploadpack.allowFilter=true",
+		"upload-pack",
+		"--stateless-rpc",
+		".",
+	}...)
+	cmd.Dir = c.Dir
+	cmd.SysProcAttr = &syscall.SysProcAttr{Setpgid: true}
+
+	stdoutPipe, _ := cmd.StdoutPipe()
+	cmd.Stderr = cmd.Stdout
+	defer stdoutPipe.Close()
+
+	stdinPipe, err := cmd.StdinPipe()
+	if err != nil {
+		return err
+	}
+	defer stdinPipe.Close()
+
+	if err := cmd.Start(); err != nil {
+		log.Printf("git: failed to start git-upload-pack: %s", err)
+		return err
+	}
+
+	if _, err := io.Copy(stdinPipe, c.Stdin); err != nil {
+		log.Printf("git: failed to copy stdin: %s", err)
+		return err
+	}
+	stdinPipe.Close()
+
+	if _, err := io.Copy(newWriteFlusher(c.Stdout), stdoutPipe); err != nil {
+		log.Printf("git: failed to copy stdout: %s", err)
+		return err
+	}
+	if err := cmd.Wait(); err != nil {
+		log.Printf("git: failed to wait for git-upload-pack: %s", err)
+		return err
+	}
+
+	return nil
+}
+
+func packLine(w io.Writer, s string) error {
+	_, err := fmt.Fprintf(w, "%04x%s", len(s)+4, s)
+	return err
+}
+
+func packFlush(w io.Writer) error {
+	_, err := fmt.Fprint(w, "0000")
+	return err
+}
diff --git a/git/service/write_flusher.go b/git/service/write_flusher.go
new file mode 100644
index 0000000..f25a5ae
--- /dev/null
+++ b/git/service/write_flusher.go
@@ -0,0 +1,25 @@
+package service
+
+import (
+	"io"
+	"net/http"
+)
+
+func newWriteFlusher(w http.ResponseWriter) io.Writer {
+	return writeFlusher{w.(interface {
+		io.Writer
+		http.Flusher
+	})}
+}
+
+type writeFlusher struct {
+	wf interface {
+		io.Writer
+		http.Flusher
+	}
+}
+
+func (w writeFlusher) Write(p []byte) (int, error) {
+	defer w.wf.Flush()
+	return w.wf.Write(p)
+}