adds help for load command (#383)

* adds help for load command

Signed-off-by: Mike Brown <brownwm@us.ibm.com>

* vendor restrom/dedent

Signed-off-by: Mike Brown <brownwm@us.ibm.com>

cmd/cri-containerd/cri_containerd.go

@@ -26,11 +26,13 @@ import (
 	"os/signal"
 	"path/filepath"
 	"runtime"
+	"strings"
 	"syscall"
 
 	"github.com/docker/docker/pkg/reexec"
 	"github.com/golang/glog"
 	"github.com/opencontainers/selinux/go-selinux"
+	"github.com/renstrom/dedent"
 	"github.com/spf13/cobra"
 	"golang.org/x/net/context"
 	"k8s.io/kubernetes/pkg/util/interrupt"
@@ -58,6 +60,30 @@ var cmd = &cobra.Command{
 	Long:  desc,
 }
 
+var (
+	loadLong = dedent.Dedent(`
+		Help for "load TAR" command
+
+		TAR - The path to a tar archive containing a container image.
+
+		Requirement:
+			Containerd and cri-containerd daemons (grpc servers) must already be up and
+			running before the load command is used.
+
+		Description:
+			Running as a client, cri-containerd implements the load command by sending the
+			load request to the already running cri-containerd daemon/server, which in
+			turn loads the image into containerd's image storage via the already running
+			containerd daemon.`)
+
+	loadExample = dedent.Dedent(`
+		- use docker to pull the latest busybox image and save it as a tar archive:
+			$ docker pull busybox:latest
+			$ docker save busybox:latest -o busybox.tar
+		- use cri-containerd to load the image into containerd's image storage:
+			$ cri-containerd load busybox.tar`)
+)
+
 // Add golang flags as persistent flags.
 func init() {
 	cmd.PersistentFlags().AddGoFlagSet(flag.CommandLine)
@@ -85,10 +111,13 @@ func versionCommand() *cobra.Command {
 
 func loadImageCommand() *cobra.Command {
 	c := &cobra.Command{
-		Use:   "load TAR",
-		Short: "Load an image from a tar archive.",
-		Args:  cobra.ExactArgs(1),
+		Use:     "load TAR",
+		Long:    loadLong,
+		Short:   "Load an image from a tar archive.",
+		Args:    cobra.ExactArgs(1),
+		Example: loadExample,
 	}
+	c.SetUsageTemplate(strings.Replace(c.UsageTemplate(), "Examples:", "Example:", 1))
 	endpoint, timeout := options.AddGRPCFlags(c.Flags())
 	c.RunE = func(cmd *cobra.Command, args []string) error {
 		cl, err := client.NewCRIContainerdClient(*endpoint, *timeout)