Disable update for windows for the time being

Signed-off-by: Alex Ellis (OpenFaaS Ltd) <alexellis2@gmail.com>

README.md

@@ -145,7 +145,7 @@ Arkade can be used to install Kubernetes apps or to download CLI tools.
 * `arkade install` - install a Kubernetes app
 * `arkade info` - see the post installation screen for a Kubernetes app
 * `arkade get` - download a CLI tool
-* `arkade update` - update arkade itself
+* `arkade update` - perform a self-update of arkade on MacOS and Linux
 
 An arkade "app" could represent a helm chart such as `openfaas/faas-netes`, a custom CLI installer such as `istioctl` or a set of static manifests (i.e. MetalLB).
 

cmd/update.go

@@ -5,6 +5,7 @@ package cmd
 
 import (
 	"fmt"
+	"runtime"
 	"strings"
 
 	"github.com/alexellis/arkade/pkg"
@@ -40,6 +41,10 @@ version twice.`,
 
 	command.RunE = func(cmd *cobra.Command, args []string) error {
 
+		if runtime.GOOS == "windows" {
+			return fmt.Errorf("update is not supported on Windows at this time")
+		}
+
 		verifyDigest, _ := cmd.Flags().GetBool("verify")
 		forceDownload, _ := cmd.Flags().GetBool("force")