fix(helm): add dry-run flag for init

This adds a --dry-run flag to init, and causes the manifest file for
Tiller to be emitted on --debug. Together, this means you can do a
'helm init --dry-run --debug' and dump the Tiller manifest much as you
can with 'helm install --dry-run --debug'.

This does not require a server round-trip.

Closes #1417

cmd/helm/init.go

@@ -33,7 +33,23 @@ import (
 
 const initDesc = `
 This command installs Tiller (the helm server side component) onto your
-Kubernetes Cluster and sets up local configuration in $HELM_HOME (default: ~/.helm/)
+Kubernetes Cluster and sets up local configuration in $HELM_HOME (default ~/.helm/)
+
+As with the rest of the Helm commands, 'helm init' discovers Kubernetes clusters
+by reading $KUBECONFIG (default '~/.kube/config') and using the default context.
+
+To set up just a local environment, use '--client-only'. That will configure
+$HELM_HOME, but not attempt to connect to a remote cluster and install the Tiller
+deployment.
+
+When installing Tiller, 'helm init' will attempt to install the latest released
+version. You can specify an alternative image with '--tiller-image'. For those
+frequently working on the latest code, the flag '--canary-image' will install
+the latest pre-release version of Tiller (e.g. the HEAD commit in the GitHub
+repository on the master branch).
+
+To dump a manifest containing the Tiller deployment YAML, combine the
+'--dry-run' and '--debug' flags.
 `
 
 const (
@@ -47,6 +63,7 @@ type initCmd struct {
 	image      string
 	clientOnly bool
 	canary     bool
+	dryRun     bool
 	out        io.Writer
 	home       helmpath.Home
 	kubeClient unversioned.DeploymentsNamespacer
@@ -74,12 +91,25 @@ func newInitCmd(out io.Writer) *cobra.Command {
 	f.StringVarP(&i.image, "tiller-image", "i", "", "override tiller image")
 	f.BoolVar(&i.canary, "canary-image", false, "use the canary tiller image")
 	f.BoolVarP(&i.clientOnly, "client-only", "c", false, "if set does not install tiller")
+	f.BoolVar(&i.dryRun, "dry-run", false, "do not install local or remote")
 
 	return cmd
 }
 
 // runInit initializes local config and installs tiller to Kubernetes Cluster
 func (i *initCmd) run() error {
+
+	if flagDebug {
+		m, err := installer.DeploymentManifest(i.image, i.canary)
+		if err != nil {
+			return err
+		}
+		fmt.Fprintln(i.out, m)
+	}
+	if i.dryRun {
+		return nil
+	}
+
 	if err := ensureHome(i.home, i.out); err != nil {
 		return err
 	}

cmd/helm/init_test.go

@@ -23,6 +23,8 @@ import (
 	"strings"
 	"testing"
 
+	"github.com/ghodss/yaml"
+
 	"k8s.io/kubernetes/pkg/api"
 	"k8s.io/kubernetes/pkg/api/errors"
 	"k8s.io/kubernetes/pkg/client/unversioned/testclient"
@@ -87,7 +89,7 @@ func TestInitCmd_clientOnly(t *testing.T) {
 	fake := testclient.Fake{}
 	cmd := &initCmd{out: &buf, home: helmpath.Home(home), kubeClient: fake.Extensions(), clientOnly: true}
 	if err := cmd.run(); err != nil {
-		t.Errorf("expected error: %v", err)
+		t.Errorf("unexpected error: %v", err)
 	}
 	if len(fake.Actions()) != 0 {
 		t.Error("expected client call")
@@ -97,6 +99,42 @@ func TestInitCmd_clientOnly(t *testing.T) {
 		t.Errorf("expected %q, got %q", expected, buf.String())
 	}
 }
+
+func TestInitCmd_dryRun(t *testing.T) {
+	// This is purely defensive in this case.
+	home, err := ioutil.TempDir("", "helm_home")
+	if err != nil {
+		t.Fatal(err)
+	}
+	dbg := flagDebug
+	flagDebug = true
+	defer func() {
+		os.Remove(home)
+		flagDebug = dbg
+	}()
+
+	var buf bytes.Buffer
+	fake := testclient.Fake{}
+	cmd := &initCmd{
+		out:        &buf,
+		home:       helmpath.Home(home),
+		kubeClient: fake.Extensions(),
+		clientOnly: true,
+		dryRun:     true,
+	}
+	if err := cmd.run(); err != nil {
+		t.Fatal(err)
+	}
+	if len(fake.Actions()) != 0 {
+		t.Error("expected no server calls")
+	}
+
+	var y map[string]interface{}
+	if err := yaml.Unmarshal(buf.Bytes(), &y); err != nil {
+		t.Errorf("Expected parseable YAML, got %q\n\t%s", buf.String(), err)
+	}
+}
+
 func TestEnsureHome(t *testing.T) {
 	home, err := ioutil.TempDir("", "helm_home")
 	if err != nil {

cmd/helm/installer/install.go

@@ -19,6 +19,8 @@ package installer // import "k8s.io/helm/cmd/helm/installer"
 import (
 	"fmt"
 
+	"github.com/ghodss/yaml"
+
 	"k8s.io/kubernetes/pkg/api"
 	"k8s.io/kubernetes/pkg/apis/extensions"
 	"k8s.io/kubernetes/pkg/client/unversioned"
@@ -36,15 +38,29 @@ const defaultImage = "gcr.io/kubernetes-helm/tiller"
 //
 // If verbose is true, this will print the manifest to stdout.
 func Install(client unversioned.DeploymentsNamespacer, namespace, image string, canary, verbose bool) error {
+	obj := deployment(image, canary)
+	_, err := client.Deployments(namespace).Create(obj)
+	return err
+}
+
+// deployment gets the deployment object that installs Tiller.
+func deployment(image string, canary bool) *extensions.Deployment {
 	switch {
 	case canary:
 		image = defaultImage + ":canary"
 	case image == "":
 		image = fmt.Sprintf("%s:%s", defaultImage, version.Version)
 	}
-	obj := generateDeployment(image)
-	_, err := client.Deployments(namespace).Create(obj)
-	return err
+	return generateDeployment(image)
+}
+
+// DeploymentManifest gets the manifest (as a string) that describes the Tiller Deployment
+// resource.
+func DeploymentManifest(image string, canary bool) (string, error) {
+	obj := deployment(image, canary)
+
+	buf, err := yaml.Marshal(obj)
+	return string(buf), err
 }
 
 func generateLabels(labels map[string]string) map[string]string {

cmd/helm/installer/install_test.go

@@ -20,11 +20,45 @@ import (
 	"reflect"
 	"testing"
 
+	"github.com/ghodss/yaml"
+
+	"k8s.io/helm/pkg/version"
+
 	"k8s.io/kubernetes/pkg/apis/extensions"
 	"k8s.io/kubernetes/pkg/client/unversioned/testclient"
 	"k8s.io/kubernetes/pkg/runtime"
 )
 
+func TestDeploymentManifest(t *testing.T) {
+
+	tests := []struct {
+		name   string
+		image  string
+		canary bool
+		expect string
+	}{
+		{"default", "", false, "gcr.io/kubernetes-helm/tiller:" + version.Version},
+		{"canary", "example.com/tiller", true, "gcr.io/kubernetes-helm/tiller:canary"},
+		{"custom", "example.com/tiller:latest", false, "example.com/tiller:latest"},
+	}
+
+	for _, tt := range tests {
+
+		o, err := DeploymentManifest(tt.image, tt.canary)
+		if err != nil {
+			t.Fatalf("%s: error %q", tt.name, err)
+		}
+		var dep extensions.Deployment
+		if err := yaml.Unmarshal([]byte(o), &dep); err != nil {
+			t.Fatalf("%s: error %q", tt.name, err)
+		}
+
+		if got := dep.Spec.Template.Spec.Containers[0].Image; got != tt.expect {
+			t.Errorf("%s: expected image %q, got %q", tt.name, tt.expect, got)
+		}
+	}
+}
+
 func TestInstall(t *testing.T) {
 	image := "gcr.io/kubernetes-helm/tiller:v2.0.0"