fix: set MagicDir to tempdir when performing cache probe (#48)

* fix: set MagicDir to tempdir when performing cache probe

* chore: update envbuilder to b7781d8

* imgutil: get default envbuilder binary path from envbuilder options

testutil/registrytest/registrytest.go

@@ -2,6 +2,7 @@ package registrytest
 
 import (
 	"fmt"
+	"net/http"
 	"net/http/httptest"
 	"net/url"
 	"testing"
@@ -13,12 +14,31 @@ import (
 // New starts a new Docker registry listening on localhost.
 // It will automatically shut down when the test finishes.
 // It will store data in dir.
-func New(t testing.TB, dir string) string {
+func New(t testing.TB, dir string, mws ...func(http.Handler) http.Handler) string {
 	t.Helper()
 	regHandler := registry.New(registry.WithBlobHandler(registry.NewDiskBlobHandler(dir)))
+	for _, mw := range mws {
+		regHandler = mw(regHandler)
+	}
 	regSrv := httptest.NewServer(regHandler)
 	t.Cleanup(func() { regSrv.Close() })
 	regSrvURL, err := url.Parse(regSrv.URL)
 	require.NoError(t, err)
 	return fmt.Sprintf("localhost:%s", regSrvURL.Port())
 }
+
+func BasicAuthMW(t testing.TB, username, password string) func(http.Handler) http.Handler {
+	return func(next http.Handler) http.Handler {
+		return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+			if username != "" || password != "" {
+				authUser, authPass, ok := r.BasicAuth()
+				if !ok || username != authUser || password != authPass {
+					t.Logf("basic auth failed: got user %q, pass %q", authUser, authPass)
+					w.WriteHeader(http.StatusUnauthorized)
+					return
+				}
+			}
+			next.ServeHTTP(w, r)
+		})
+	}
+}