Fix kubeconfig load from multiple configuration files (#301)

* fix kubeconfig load with standards kubectl approach

* update cli docs

cli/cmds/cluster_create.go

@@ -67,7 +67,7 @@ func createAction(config *CreateConfig) cli.ActionFunc {
 			return errors.New("invalid cluster name")
 		}
 
-		restConfig, err := clientcmd.BuildConfigFromFlags("", Kubeconfig)
+		restConfig, err := loadRESTConfig()
 		if err != nil {
 			return err
 		}

cli/cmds/cluster_delete.go

@@ -9,7 +9,6 @@ import (
 	"github.com/sirupsen/logrus"
 	"github.com/urfave/cli/v2"
 	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
-	"k8s.io/client-go/tools/clientcmd"
 	"sigs.k8s.io/controller-runtime/pkg/client"
 )
 
@@ -36,7 +35,7 @@ func delete(clx *cli.Context) error {
 		return errors.New("invalid cluster name")
 	}
 
-	restConfig, err := clientcmd.BuildConfigFromFlags("", Kubeconfig)
+	restConfig, err := loadRESTConfig()
 	if err != nil {
 		return err
 	}

cli/cmds/kubeconfig.go

@@ -92,11 +92,7 @@ func NewKubeconfigCommand() *cli.Command {
 }
 
 func generate(clx *cli.Context) error {
-	var cluster v1alpha1.Cluster
-
-	ctx := context.Background()
-
-	restConfig, err := clientcmd.BuildConfigFromFlags("", Kubeconfig)
+	restConfig, err := loadRESTConfig()
 	if err != nil {
 		return err
 	}
@@ -113,6 +109,9 @@ func generate(clx *cli.Context) error {
 		Namespace: Namespace(),
 	}
 
+	var cluster v1alpha1.Cluster
+
+	ctx := context.Background()
 	if err := ctrlClient.Get(ctx, clusterKey, &cluster); err != nil {
 		return err
 	}

cli/cmds/root.go

@@ -2,7 +2,6 @@ package cmds
 
 import (
 	"fmt"
-	"os"
 
 	"github.com/rancher/k3k/pkg/apis/k3k.io/v1alpha1"
 	"github.com/rancher/k3k/pkg/buildinfo"
@@ -10,6 +9,8 @@ import (
 	"github.com/urfave/cli/v2"
 	"k8s.io/apimachinery/pkg/runtime"
 	clientgoscheme "k8s.io/client-go/kubernetes/scheme"
+	"k8s.io/client-go/rest"
+	"k8s.io/client-go/tools/clientcmd"
 )
 
 const (
@@ -26,11 +27,9 @@ var (
 	CommonFlags = []cli.Flag{
 		&cli.StringFlag{
 			Name:        "kubeconfig",
-			EnvVars:     []string{"KUBECONFIG"},
 			Usage:       "kubeconfig path",
 			Destination: &Kubeconfig,
-			Value:       os.Getenv("HOME") + "/.kube/config",
-			DefaultText: "$HOME/.kube/config",
+			DefaultText: "$HOME/.kube/config or $KUBECONFIG if set",
 		},
 		&cli.StringFlag{
 			Name:        "namespace",
@@ -86,3 +85,16 @@ func Namespace() string {
 
 	return namespace
 }
+
+func loadRESTConfig() (*rest.Config, error) {
+	loadingRules := clientcmd.NewDefaultClientConfigLoadingRules()
+	configOverrides := &clientcmd.ConfigOverrides{}
+
+	if Kubeconfig != "" {
+		loadingRules.ExplicitPath = Kubeconfig
+	}
+
+	kubeConfig := clientcmd.NewNonInteractiveDeferredLoadingClientConfig(loadingRules, configOverrides)
+
+	return kubeConfig.ClientConfig()
+}