vendor: update buildkit to v0.8

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

vendor/github.com/docker/cli/cli-plugins/manager/manager.go

@@ -1,7 +1,6 @@
 package manager
 
 import (
-	"fmt"
 	"io/ioutil"
 	"os"
 	"os/exec"
@@ -30,16 +29,6 @@ func (e errPluginNotFound) Error() string {
 	return "Error: No such CLI plugin: " + string(e)
 }
 
-type errPluginRequireExperimental string
-
-// Note: errPluginRequireExperimental implements notFound so that the plugin
-// is skipped when listing the plugins.
-func (e errPluginRequireExperimental) NotFound() {}
-
-func (e errPluginRequireExperimental) Error() string {
-	return fmt.Sprintf("plugin candidate %q: requires experimental CLI", string(e))
-}
-
 type notFound interface{ NotFound() }
 
 // IsNotFound is true if the given error is due to a plugin not being found.
@@ -133,7 +122,7 @@ func ListPlugins(dockerCli command.Cli, rootcmd *cobra.Command) ([]Plugin, error
 			continue
 		}
 		c := &candidate{paths[0]}
-		p, err := newPlugin(c, rootcmd, dockerCli.ClientInfo().HasExperimental)
+		p, err := newPlugin(c, rootcmd)
 		if err != nil {
 			return nil, err
 		}
@@ -181,19 +170,12 @@ func PluginRunCommand(dockerCli command.Cli, name string, rootcmd *cobra.Command
 		}
 
 		c := &candidate{path: path}
-		plugin, err := newPlugin(c, rootcmd, dockerCli.ClientInfo().HasExperimental)
+		plugin, err := newPlugin(c, rootcmd)
 		if err != nil {
 			return nil, err
 		}
 		if plugin.Err != nil {
 			// TODO: why are we not returning plugin.Err?
-
-			err := plugin.Err.(*pluginError).Cause()
-			// if an experimental plugin was invoked directly while experimental mode is off
-			// provide a more useful error message than "not found".
-			if err, ok := err.(errPluginRequireExperimental); ok {
-				return nil, err
-			}
 			return nil, errPluginNotFound(name)
 		}
 		cmd := exec.Command(plugin.Path, args...)

vendor/github.com/docker/cli/cli-plugins/manager/metadata.go

@@ -23,6 +23,6 @@ type Metadata struct {
 	// URL is a pointer to the plugin's homepage.
 	URL string `json:",omitempty"`
 	// Experimental specifies whether the plugin is experimental.
-	// Experimental plugins are not displayed on non-experimental CLIs.
+	// Deprecated: experimental features are now always enabled in the CLI
 	Experimental bool `json:",omitempty"`
 }

vendor/github.com/docker/cli/cli-plugins/manager/plugin.go

@@ -35,7 +35,7 @@ type Plugin struct {
 // non-recoverable error.
 //
 // nolint: gocyclo
-func newPlugin(c Candidate, rootcmd *cobra.Command, allowExperimental bool) (Plugin, error) {
+func newPlugin(c Candidate, rootcmd *cobra.Command) (Plugin, error) {
 	path := c.Path()
 	if path == "" {
 		return Plugin{}, errors.New("plugin candidate path cannot be empty")
@@ -96,10 +96,6 @@ func newPlugin(c Candidate, rootcmd *cobra.Command, allowExperimental bool) (Plu
 		p.Err = wrapAsPluginError(err, "invalid metadata")
 		return p, nil
 	}
-	if p.Experimental && !allowExperimental {
-		p.Err = &pluginError{errPluginRequireExperimental(p.Name)}
-		return p, nil
-	}
 	if p.Metadata.SchemaVersion != "0.1.0" {
 		p.Err = NewPluginError("plugin SchemaVersion %q is not valid, must be 0.1.0", p.Metadata.SchemaVersion)
 		return p, nil