avoid import to testing helpers outside of tests

Signed-off-by: Tonis Tiigi <tonistiigi@gmail.com>

util/gitutil/gittestutil/testutilserve.go

@@ -0,0 +1,99 @@
+package gittestutil
+
+import (
+	"context"
+	"fmt"
+	"net"
+	"net/http"
+	"testing"
+
+	"github.com/docker/buildx/util/gitutil"
+	"github.com/pkg/errors"
+	"github.com/stretchr/testify/require"
+)
+
+type gitServe struct {
+	token string
+}
+
+type GitServeOpt func(*gitServe)
+
+func WithAccessToken(token string) GitServeOpt {
+	return func(s *gitServe) {
+		s.token = token
+	}
+}
+
+func GitServeHTTP(c *gitutil.Git, t testing.TB, opts ...GitServeOpt) (url string) {
+	t.Helper()
+	gitUpdateServerInfo(c, t)
+	ctx, cancel := context.WithCancelCause(context.TODO())
+
+	gs := &gitServe{}
+	for _, opt := range opts {
+		opt(gs)
+	}
+
+	ready := make(chan struct{})
+	done := make(chan struct{})
+
+	name := "test.git"
+	dir, err := c.GitDir()
+	if err != nil {
+		cancel(err)
+	}
+
+	var addr string
+	go func() {
+		mux := http.NewServeMux()
+		prefix := fmt.Sprintf("/%s/", name)
+
+		handler := func(next http.Handler) http.Handler {
+			var tokenChecked bool
+			return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+				if gs.token != "" && !tokenChecked {
+					t.Logf("git access token to check: %q", gs.token)
+					user, pass, _ := r.BasicAuth()
+					t.Logf("basic auth: user=%q pass=%q", user, pass)
+					if pass != gs.token {
+						http.Error(w, "Unauthorized", http.StatusUnauthorized)
+						return
+					}
+					tokenChecked = true
+				}
+				next.ServeHTTP(w, r)
+			})
+		}
+
+		mux.Handle(prefix, handler(http.StripPrefix(prefix, http.FileServer(http.Dir(dir)))))
+		l, err := net.Listen("tcp", "localhost:0")
+		if err != nil {
+			panic(err)
+		}
+
+		addr = l.Addr().String()
+
+		close(ready)
+
+		s := http.Server{Handler: mux} //nolint:gosec // potential attacks are not relevant for tests
+		go s.Serve(l)
+		<-ctx.Done()
+		s.Shutdown(context.TODO())
+		l.Close()
+
+		close(done)
+	}()
+	<-ready
+
+	t.Cleanup(func() {
+		cancel(errors.Errorf("cleanup"))
+		<-done
+	})
+	return fmt.Sprintf("http://%s/%s", addr, name)
+}
+
+func gitUpdateServerInfo(c *gitutil.Git, tb testing.TB) {
+	tb.Helper()
+	_, err := fakeGit(c, "update-server-info")
+	require.NoError(tb, err)
+}