Update ctr containers and tasks command

This moves container and tasks commands under the containers and tasks
top level commands.

Signed-off-by: Michael Crosby <crosbymichael@gmail.com>

cmd/ctr/containers.go

@@ -0,0 +1,77 @@
+package main
+
+import (
+	"fmt"
+	"os"
+	"strings"
+	"text/tabwriter"
+
+	"github.com/urfave/cli"
+)
+
+var containersCommand = cli.Command{
+	Name:    "containers",
+	Usage:   "manage containers (metadata)",
+	Aliases: []string{"c"},
+	Flags: []cli.Flag{
+		cli.BoolFlag{
+			Name:  "quiet, q",
+			Usage: "print only the container id",
+		},
+	},
+	Subcommands: []cli.Command{
+		containersDeleteCommand,
+		containersSetLabelsCommand,
+		containerInfoCommand,
+	},
+	ArgsUsage: "[filter, ...]",
+	Action: func(context *cli.Context) error {
+		var (
+			filters     = context.Args()
+			quiet       = context.Bool("quiet")
+			ctx, cancel = appContext(context)
+		)
+		defer cancel()
+
+		client, err := newClient(context)
+		if err != nil {
+			return err
+		}
+		containers, err := client.Containers(ctx, filters...)
+		if err != nil {
+			return err
+		}
+		if quiet {
+			for _, c := range containers {
+				fmt.Printf("%s\n", c.ID())
+			}
+			return nil
+		}
+		w := tabwriter.NewWriter(os.Stdout, 4, 8, 4, ' ', 0)
+		fmt.Fprintln(w, "CONTAINER\tIMAGE\tRUNTIME\tLABELS\t")
+		for _, c := range containers {
+			var labelStrings []string
+			for k, v := range c.Info().Labels {
+				labelStrings = append(labelStrings, strings.Join([]string{k, v}, "="))
+			}
+			labels := strings.Join(labelStrings, ",")
+			if labels == "" {
+				labels = "-"
+			}
+			imageName := c.Info().Image
+			if imageName == "" {
+				imageName = "-"
+			}
+			record := c.Info()
+			if _, err := fmt.Fprintf(w, "%s\t%s\t%s\t%v\t\n",
+				c.ID(),
+				imageName,
+				record.Runtime.Name,
+				labels,
+			); err != nil {
+				return err
+			}
+		}
+		return w.Flush()
+	},
+}