vendor: update moby/buildkit

Update modules:

  go mod edit -require github.com/moby/buildkit@master
  go mod tidy -compat=1.17 && ./hack/update-vendor

Signed-off-by: Justin Chadwell <me@jedevc.com>

vendor/github.com/moby/buildkit/client/connhelper/kubepod/kubepod.go

@@ -0,0 +1,78 @@
+// Package kubepod provides connhelper for kube-pod://<pod>
+package kubepod
+
+import (
+	"context"
+	"net"
+	"net/url"
+	"regexp"
+
+	"github.com/docker/cli/cli/connhelper/commandconn"
+	"github.com/moby/buildkit/client/connhelper"
+	"github.com/pkg/errors"
+)
+
+func init() {
+	connhelper.Register("kube-pod", Helper)
+}
+
+// Helper returns helper for connecting to a Kubernetes pod.
+// Requires BuildKit v0.5.0 or later in the pod.
+func Helper(u *url.URL) (*connhelper.ConnectionHelper, error) {
+	sp, err := SpecFromURL(u)
+	if err != nil {
+		return nil, err
+	}
+	return &connhelper.ConnectionHelper{
+		ContextDialer: func(ctx context.Context, addr string) (net.Conn, error) {
+			// using background context because context remains active for the duration of the process, after dial has completed
+			return commandconn.New(context.Background(), "kubectl", "--context="+sp.Context, "--namespace="+sp.Namespace,
+				"exec", "--container="+sp.Container, "-i", sp.Pod, "--", "buildctl", "dial-stdio")
+		},
+	}, nil
+}
+
+// Spec
+type Spec struct {
+	Context   string
+	Namespace string
+	Pod       string
+	Container string
+}
+
+// SpecFromURL creates Spec from URL.
+// URL is like kube-pod://<pod>?context=<context>&namespace=<namespace>&container=<container> .
+// Only <pod> part is mandatory.
+func SpecFromURL(u *url.URL) (*Spec, error) {
+	q := u.Query()
+	sp := Spec{
+		Context:   q.Get("context"),
+		Namespace: q.Get("namespace"),
+		Pod:       u.Hostname(),
+		Container: q.Get("container"),
+	}
+	if sp.Context != "" && !validKubeIdentifier(sp.Context) {
+		return nil, errors.Errorf("unsupported context name: %q", sp.Context)
+	}
+	if sp.Namespace != "" && !validKubeIdentifier(sp.Namespace) {
+		return nil, errors.Errorf("unsupported namespace name: %q", sp.Namespace)
+	}
+	if sp.Pod == "" {
+		return nil, errors.New("url lacks pod name")
+	}
+	if !validKubeIdentifier(sp.Pod) {
+		return nil, errors.Errorf("unsupported pod name: %q", sp.Pod)
+	}
+	if sp.Container != "" && !validKubeIdentifier(sp.Container) {
+		return nil, errors.Errorf("unsupported container name: %q", sp.Container)
+	}
+	return &sp, nil
+}
+
+var kubeIdentifierRegexp = regexp.MustCompile(`^[-a-z0-9.]+$`)
+
+// validKubeIdentifier: https://kubernetes.io/docs/concepts/overview/working-with-objects/names/#names
+// The length is not checked because future version of Kube may support longer identifiers.
+func validKubeIdentifier(s string) bool {
+	return kubeIdentifierRegexp.MatchString(s)
+}