Add 'containerd config dump' subcommand

Signed-off-by: Maksym Pavlenko <makpav@amazon.com>

cmd/containerd/command/config.go

@@ -40,17 +40,11 @@ func (c *Config) WriteTo(w io.Writer) (int64, error) {
 	return 0, toml.NewEncoder(w).Encode(c)
 }
 
-var configCommand = cli.Command{
+func outputConfig(cfg *srvconfig.Config) error {
-	Name:  "config",
-	Usage: "information on the containerd config",
-	Subcommands: []cli.Command{
-		{
-			Name:  "default",
-			Usage: "see the output of the default config",
-			Action: func(context *cli.Context) error {
 	config := &Config{
-					Config: defaultConfig(),
+		Config: cfg,
 	}
+
 	// for the time being, keep the defaultConfig's version set at 1 so that
 	// when a config without a version is loaded from disk and has no version
 	// set, we assume it's a v1 config.  But when generating new configs via
@@ -77,6 +71,29 @@ var configCommand = cli.Command{
 
 	_, err = config.WriteTo(os.Stdout)
 	return err
+}
+
+var configCommand = cli.Command{
+	Name:  "config",
+	Usage: "information on the containerd config",
+	Subcommands: []cli.Command{
+		{
+			Name:  "default",
+			Usage: "see the output of the default config",
+			Action: func(context *cli.Context) error {
+				return outputConfig(defaultConfig())
+			},
+		},
+		{
+			Name:  "dump",
+			Usage: "see the output of the final main config with imported in subconfig files",
+			Action: func(context *cli.Context) error {
+				config := defaultConfig()
+				if err := srvconfig.LoadConfig(context.GlobalString("config"), config); err != nil && !os.IsNotExist(err) {
+					return err
+				}
+
+				return outputConfig(config)
 			},
 		},
 	},