Add inspect image commands

Outputs the image structure as a tree with an option to show content
and related labels for the image.

Signed-off-by: Derek McGowan <derek@mcg.dev>

cmd/ctr/commands/images/images.go

@@ -42,6 +42,7 @@ var Command = cli.Command{
 		checkCommand,
 		exportCommand,
 		importCommand,
+		inspectCommand,
 		listCommand,
 		mountCommand,
 		unmountCommand,

cmd/ctr/commands/images/inspect.go

@@ -0,0 +1,65 @@
+/*
+   Copyright 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 images
+
+import (
+	"os"
+
+	"github.com/containerd/containerd/cmd/ctr/commands"
+	"github.com/containerd/containerd/pkg/display"
+	"github.com/urfave/cli"
+)
+
+var inspectCommand = cli.Command{
+	Name:        "inspect",
+	Aliases:     []string{"i"},
+	Usage:       "inspect an image",
+	ArgsUsage:   "<image> [flags]",
+	Description: `Inspect an image`,
+	Flags: []cli.Flag{
+		cli.BoolFlag{
+			Name:  "content",
+			Usage: "Show JSON content",
+		},
+	},
+	Action: func(clicontext *cli.Context) error {
+		client, ctx, cancel, err := commands.NewClient(clicontext)
+		if err != nil {
+			return err
+		}
+		defer cancel()
+		var (
+			ref        = clicontext.Args().First()
+			imageStore = client.ImageService()
+			cs         = client.ContentStore()
+		)
+
+		img, err := imageStore.Get(ctx, ref)
+		if err != nil {
+			return err
+		}
+
+		opts := []display.PrintOpt{
+			display.WithWriter(os.Stdout),
+		}
+		if clicontext.Bool("content") {
+			opts = append(opts, display.Verbose)
+		}
+
+		return display.NewImageTreePrinter(opts...).PrintImageTree(ctx, img, cs)
+	},
+}