Import of https://github.com/ciena/voltctl at commit 40d61fbf3f910ed4017cf67c9c79e8e1f82a33a5

Change-Id: I8464c59e60d76cb8612891db3303878975b5416c
diff --git a/vendor/k8s.io/client-go/tools/clientcmd/merged_client_builder.go b/vendor/k8s.io/client-go/tools/clientcmd/merged_client_builder.go
new file mode 100644
index 0000000..9cc112a
--- /dev/null
+++ b/vendor/k8s.io/client-go/tools/clientcmd/merged_client_builder.go
@@ -0,0 +1,173 @@
+/*
+Copyright 2014 The Kubernetes Authors.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package clientcmd
+
+import (
+	"io"
+	"sync"
+
+	"k8s.io/klog"
+
+	restclient "k8s.io/client-go/rest"
+	clientcmdapi "k8s.io/client-go/tools/clientcmd/api"
+)
+
+// DeferredLoadingClientConfig is a ClientConfig interface that is backed by a client config loader.
+// It is used in cases where the loading rules may change after you've instantiated them and you want to be sure that
+// the most recent rules are used.  This is useful in cases where you bind flags to loading rule parameters before
+// the parse happens and you want your calling code to be ignorant of how the values are being mutated to avoid
+// passing extraneous information down a call stack
+type DeferredLoadingClientConfig struct {
+	loader         ClientConfigLoader
+	overrides      *ConfigOverrides
+	fallbackReader io.Reader
+
+	clientConfig ClientConfig
+	loadingLock  sync.Mutex
+
+	// provided for testing
+	icc InClusterConfig
+}
+
+// InClusterConfig abstracts details of whether the client is running in a cluster for testing.
+type InClusterConfig interface {
+	ClientConfig
+	Possible() bool
+}
+
+// NewNonInteractiveDeferredLoadingClientConfig creates a ConfigClientClientConfig using the passed context name
+func NewNonInteractiveDeferredLoadingClientConfig(loader ClientConfigLoader, overrides *ConfigOverrides) ClientConfig {
+	return &DeferredLoadingClientConfig{loader: loader, overrides: overrides, icc: &inClusterClientConfig{overrides: overrides}}
+}
+
+// NewInteractiveDeferredLoadingClientConfig creates a ConfigClientClientConfig using the passed context name and the fallback auth reader
+func NewInteractiveDeferredLoadingClientConfig(loader ClientConfigLoader, overrides *ConfigOverrides, fallbackReader io.Reader) ClientConfig {
+	return &DeferredLoadingClientConfig{loader: loader, overrides: overrides, icc: &inClusterClientConfig{overrides: overrides}, fallbackReader: fallbackReader}
+}
+
+func (config *DeferredLoadingClientConfig) createClientConfig() (ClientConfig, error) {
+	if config.clientConfig == nil {
+		config.loadingLock.Lock()
+		defer config.loadingLock.Unlock()
+
+		if config.clientConfig == nil {
+			mergedConfig, err := config.loader.Load()
+			if err != nil {
+				return nil, err
+			}
+
+			var mergedClientConfig ClientConfig
+			if config.fallbackReader != nil {
+				mergedClientConfig = NewInteractiveClientConfig(*mergedConfig, config.overrides.CurrentContext, config.overrides, config.fallbackReader, config.loader)
+			} else {
+				mergedClientConfig = NewNonInteractiveClientConfig(*mergedConfig, config.overrides.CurrentContext, config.overrides, config.loader)
+			}
+
+			config.clientConfig = mergedClientConfig
+		}
+	}
+
+	return config.clientConfig, nil
+}
+
+func (config *DeferredLoadingClientConfig) RawConfig() (clientcmdapi.Config, error) {
+	mergedConfig, err := config.createClientConfig()
+	if err != nil {
+		return clientcmdapi.Config{}, err
+	}
+
+	return mergedConfig.RawConfig()
+}
+
+// ClientConfig implements ClientConfig
+func (config *DeferredLoadingClientConfig) ClientConfig() (*restclient.Config, error) {
+	mergedClientConfig, err := config.createClientConfig()
+	if err != nil {
+		return nil, err
+	}
+
+	// load the configuration and return on non-empty errors and if the
+	// content differs from the default config
+	mergedConfig, err := mergedClientConfig.ClientConfig()
+	switch {
+	case err != nil:
+		if !IsEmptyConfig(err) {
+			// return on any error except empty config
+			return nil, err
+		}
+	case mergedConfig != nil:
+		// the configuration is valid, but if this is equal to the defaults we should try
+		// in-cluster configuration
+		if !config.loader.IsDefaultConfig(mergedConfig) {
+			return mergedConfig, nil
+		}
+	}
+
+	// check for in-cluster configuration and use it
+	if config.icc.Possible() {
+		klog.V(4).Infof("Using in-cluster configuration")
+		return config.icc.ClientConfig()
+	}
+
+	// return the result of the merged client config
+	return mergedConfig, err
+}
+
+// Namespace implements KubeConfig
+func (config *DeferredLoadingClientConfig) Namespace() (string, bool, error) {
+	mergedKubeConfig, err := config.createClientConfig()
+	if err != nil {
+		return "", false, err
+	}
+
+	ns, overridden, err := mergedKubeConfig.Namespace()
+	// if we get an error and it is not empty config, or if the merged config defined an explicit namespace, or
+	// if in-cluster config is not possible, return immediately
+	if (err != nil && !IsEmptyConfig(err)) || overridden || !config.icc.Possible() {
+		// return on any error except empty config
+		return ns, overridden, err
+	}
+
+	if len(ns) > 0 {
+		// if we got a non-default namespace from the kubeconfig, use it
+		if ns != "default" {
+			return ns, false, nil
+		}
+
+		// if we got a default namespace, determine whether it was explicit or implicit
+		if raw, err := mergedKubeConfig.RawConfig(); err == nil {
+			// determine the current context
+			currentContext := raw.CurrentContext
+			if config.overrides != nil && len(config.overrides.CurrentContext) > 0 {
+				currentContext = config.overrides.CurrentContext
+			}
+			if context := raw.Contexts[currentContext]; context != nil && len(context.Namespace) > 0 {
+				return ns, false, nil
+			}
+		}
+	}
+
+	klog.V(4).Infof("Using in-cluster namespace")
+
+	// allow the namespace from the service account token directory to be used.
+	return config.icc.Namespace()
+}
+
+// ConfigAccess implements ClientConfig
+func (config *DeferredLoadingClientConfig) ConfigAccess() ConfigAccess {
+	return config.loader
+}