Add '--force' flag when switching from 'Ignore' to 'Propagate' mode

If the user switch the propagation mode directly from 'Ignore' to
'Propagate', it will fail with an error message telling the user that a
'--force' flag is needed. '-f' is also supported as a shorthand.

Tested: make test-e2e

incubator/hnc/internal/kubectl/configset.go

@@ -17,6 +17,7 @@ package kubectl
 
 import (
 	"fmt"
+	"os"
 
 	"github.com/spf13/cobra"
 
@@ -37,12 +38,21 @@ var setTypeCmd = &cobra.Command{
 		flags := cmd.Flags()
 		apiVersion, _ := flags.GetString("apiVersion")
 		kind, _ := flags.GetString("kind")
+		force, _ := flags.GetBool("force")
 		config := client.getHNCConfig()
 
 		exist := false
 		for i := 0; i < len(config.Spec.Types); i++ {
 			t := &config.Spec.Types[i]
 			if t.APIVersion == apiVersion && t.Kind == kind {
+				if t.Mode == api.Ignore && mode == api.Propagate && !force {
+					fmt.Println("Switching directly from 'Ignore' to 'Propagate' mode might cause source overwriting conflict.")
+					fmt.Println("If you are sure you want to proceed with this operation, use the '--force' flag.")
+					fmt.Println("If you are not sure and would like to see what source objects would be overwritten," +
+							"please switch to 'Remove' first. Wait 10s before switching it to 'Propagate', which will" +
+							" list all the conflicts that you can resolve them by hand.")
+					os.Exit(1)
+				}
 				t.Mode = mode
 				exist = true
 				break
@@ -65,5 +75,6 @@ var setTypeCmd = &cobra.Command{
 func newSetTypeCmd() *cobra.Command {
 	setTypeCmd.Flags().String("apiVersion", "", "API version of the kind")
 	setTypeCmd.Flags().String("kind", "", "Kind to be configured")
+	setTypeCmd.Flags().BoolP("force", "f", false, "Force to set the propagation mode")
 	return setTypeCmd
 }

incubator/hnc/test/e2e/kubectl_test.go

@@ -0,0 +1,16 @@
+package e2e
+
+import (
+	. "github.com/onsi/ginkgo"
+	. "sigs.k8s.io/multi-tenancy/incubator/hnc/pkg/testutils"
+)
+
+var _ = Describe("HNS set-config", func() {
+	It("Should use '--force' flag to change from 'Ignore' to 'Propagate'", func() {
+		MustRun("kubectl hns config set-type --apiVersion v1 --kind Secret Ignore")
+		MustNotRun("kubectl hns config set-type --apiVersion v1 --kind Secret Propagate")
+		MustRun("kubectl hns config set-type --apiVersion v1 --kind Secret Propagate --force")
+		// check that we don't need '--force' flag when changing it back
+		MustRun("kubectl hns config set-type --apiVersion v1 --kind Secret Ignore")
+	})
+})