if err != nil {
		return err
	}
	if msg.Flags&FlagSubroute != 0 {
		if m.subroute == nil {
			return fmt.Errorf("internal error: subroute not defined on client")
		}
		hid := m.subroute.withHandler(msg.Handler)
		before := len(dst)
		dst = append(dst, hid[:]...)
		if debugPrint {
			fmt.Println("Added subroute", hid.String(), "to message", msg, "len", len(dst)-before)
		}
	}

func makeSubHandlerID(id HandlerID, subRoute string) subHandlerID {
	b := subHandlerID(sha256.Sum256([]byte(subRoute)))
	b[0] = byte(id)
	b[1] = 0 // Reserved
	return b
}

func (s subHandlerID) withHandler(id HandlerID) subHandlerID {
	s[0] = byte(id)
	s[1] = 0 // Reserved
	return s
}

func (s *subHandlerID) String() string {
	if s == nil {
		return ""
	}
	return hex.EncodeToString(s[:])
}

package vcweb

import (
	"log"
	"net/http"
	"net/http/cgi"
	"os/exec"
	"runtime"
	"slices"
	"sync"
)

type gitHandler struct {
	once       sync.Once
	gitPath    string
	gitPathErr error
}

func (h *gitHandler) Available() bool {
	if runtime.GOOS == "plan9" {
		// The Git command is usually not the real Git on Plan 9.
		// See https://golang.org/issues/29640.
		return false

		vcsHandlers: map[string]vcsHandler{
			"auth":     new(authHandler),
			"dir":      new(dirHandler),
			"bzr":      new(bzrHandler),
			"fossil":   new(fossilHandler),
			"git":      new(gitHandler),
			"hg":       new(hgHandler),
			"insecure": new(insecureHandler),
			"svn":      &svnHandler{svnRoot: workDir, logger: logger},
		},
	}