Add CLI package for ctr to use.

Signed-off-by: Lantao Liu <lantaol@google.com>

cli/cli.go

@@ -0,0 +1,78 @@
+/*
+Copyright 2018 The containerd Authors.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package cli
+
+import (
+	gocontext "context"
+	"fmt"
+	"path/filepath"
+
+	api "github.com/containerd/cri/pkg/api/v1"
+	"github.com/containerd/cri/pkg/client"
+	"github.com/pkg/errors"
+	"github.com/urfave/cli"
+)
+
+// Command is the cli command for cri plugin.
+var Command = cli.Command{
+	Name:  "cri",
+	Usage: "interact with cri plugin",
+	Subcommands: cli.Commands{
+		loadCommand,
+	},
+}
+
+var loadCommand = cli.Command{
+	Name:        "load",
+	Usage:       "load one or more images from tar archives.",
+	ArgsUsage:   "[flags] TAR [TAR, ...]",
+	Description: "load one or more images from tar archives.",
+	Flags:       []cli.Flag{},
+	Action: func(context *cli.Context) error {
+		var (
+			ctx     = gocontext.Background()
+			address = context.GlobalString("address")
+			timeout = context.GlobalDuration("timeout")
+			cancel  gocontext.CancelFunc
+		)
+		cl, err := client.NewCRIContainerdClient(address, timeout)
+		if err != nil {
+			return fmt.Errorf("failed to create grpc client: %v", err)
+		}
+		if timeout > 0 {
+			ctx, cancel = gocontext.WithTimeout(gocontext.Background(), timeout)
+		} else {
+			ctx, cancel = gocontext.WithCancel(ctx)
+		}
+		defer cancel()
+		for _, path := range context.Args() {
+			absPath, err := filepath.Abs(path)
+			if err != nil {
+				return errors.Wrap(err, "failed to get absolute path")
+			}
+			res, err := cl.LoadImage(ctx, &api.LoadImageRequest{FilePath: absPath})
+			if err != nil {
+				return errors.Wrap(err, "failed to load image")
+			}
+			images := res.GetImages()
+			for _, image := range images {
+				fmt.Println("Loaded image:", image)
+			}
+		}
+		return nil
+	},
+}