ctr: move tasks, run to commands package

Signed-off-by: Jess Valarezo <valarezo.jessica@gmail.com>

cmd/ctr/commands/tasks/kill.go

@@ -0,0 +1,62 @@
+package tasks
+
+import (
+	"github.com/containerd/containerd/cmd/ctr/commands"
+	"github.com/pkg/errors"
+	"github.com/urfave/cli"
+)
+
+// TODO:(jessvalarezo) the pid flag is not used here
+// update to be able to signal given pid
+var killCommand = cli.Command{
+	Name:      "kill",
+	Usage:     "signal a container (default: SIGTERM)",
+	ArgsUsage: "[flags] CONTAINER",
+	Flags: []cli.Flag{
+		cli.StringFlag{
+			Name:  "signal, s",
+			Value: "SIGTERM",
+			Usage: "signal to send to the container",
+		},
+		cli.IntFlag{
+			Name:  "pid",
+			Usage: "pid to kill",
+			Value: 0,
+		},
+		cli.BoolFlag{
+			Name:  "all, a",
+			Usage: "send signal to all processes inside the container",
+		},
+	},
+	Action: func(context *cli.Context) error {
+		id := context.Args().First()
+		if id == "" {
+			return errors.New("container id must be provided")
+		}
+		signal, err := commands.ParseSignal(context.String("signal"))
+		if err != nil {
+			return err
+		}
+		var (
+			pid = context.Int("pid")
+			all = context.Bool("all")
+		)
+		if pid > 0 && all {
+			return errors.New("enter a pid or all; not both")
+		}
+		client, ctx, cancel, err := commands.NewClient(context)
+		if err != nil {
+			return err
+		}
+		defer cancel()
+		container, err := client.LoadContainer(ctx, id)
+		if err != nil {
+			return err
+		}
+		task, err := container.Task(ctx, nil)
+		if err != nil {
+			return err
+		}
+		return task.Kill(ctx, signal)
+	},
+}