Merge pull request #3102 from Ace-Tang/arg_usage

ctr: fix image cmd ArgsUsage

cmd/ctr/commands/images/images.go

@@ -54,7 +54,7 @@ var listCommand = cli.Command{
 	Name:        "list",
 	Aliases:     []string{"ls"},
 	Usage:       "list images known to containerd",
-	ArgsUsage:   "[flags] <ref>",
+	ArgsUsage:   "[flags] [<filter>, ...]",
 	Description: "list images registered with containerd",
 	Flags: []cli.Flag{
 		cli.BoolFlag{
@@ -196,7 +196,7 @@ var setLabelsCommand = cli.Command{
 var checkCommand = cli.Command{
 	Name:        "check",
 	Usage:       "check that an image has all content available locally",
-	ArgsUsage:   "[flags] <ref> [<ref>, ...]",
+	ArgsUsage:   "[flags] [<filter>, ...]",
 	Description: "check that an image has all content available locally",
 	Flags:       commands.SnapshotterFlags,
 	Action: func(context *cli.Context) error {