Merge pull request #207 from WeiZhang555/provide-help

Provide more useful help information for ctr

README.md

@@ -14,7 +14,7 @@ The included `ctr` command-line tool allows you interact with the containerd dae
 $ sudo ctr containers start redis /containers/redis
 $ sudo ctr containers list
 ID                  PATH                STATUS              PROCESSES
-1                   /containers/redis   running             14063
+redis               /containers/redis   running             14063
 ```
 
 `/containers/redis` is the path to an OCI bundle. [See the docs for more information.](docs/bundle.md)

ctr/checkpoint.go

@@ -10,14 +10,24 @@ import (
 	netcontext "golang.org/x/net/context"
 )
 
-var checkpointCommand = cli.Command{
-	Name:  "checkpoints",
-	Usage: "list all checkpoints",
-	Subcommands: []cli.Command{
+var checkpointSubCmds = []cli.Command{
 	listCheckpointCommand,
 	createCheckpointCommand,
 	deleteCheckpointCommand,
-	},
+}
+
+var checkpointCommand = cli.Command{
+	Name:        "checkpoints",
+	Usage:       "list all checkpoints",
+	ArgsUsage:   "COMMAND [arguments...]",
+	Subcommands: checkpointSubCmds,
+	Description: func() string {
+		desc := "\n    COMMAND:\n"
+		for _, command := range checkpointSubCmds {
+			desc += fmt.Sprintf("    %-10.10s%s\n", command.Name, command.Usage)
+		}
+		return desc
+	}(),
 	Action: listCheckpoints,
 }
 

ctr/container.go

@@ -41,10 +41,7 @@ func getClient(ctx *cli.Context) types.APIClient {
 	return types.NewAPIClient(conn)
 }
 
-var containersCommand = cli.Command{
-	Name:  "containers",
-	Usage: "interact with running containers",
-	Subcommands: []cli.Command{
+var contSubCmds = []cli.Command{
 	execCommand,
 	killCommand,
 	listCommand,
@@ -54,7 +51,20 @@ var containersCommand = cli.Command{
 	statsCommand,
 	watchCommand,
 	updateCommand,
-	},
+}
+
+var containersCommand = cli.Command{
+	Name:        "containers",
+	Usage:       "interact with running containers",
+	ArgsUsage:   "COMMAND [arguments...]",
+	Subcommands: contSubCmds,
+	Description: func() string {
+		desc := "\n    COMMAND:\n"
+		for _, command := range contSubCmds {
+			desc += fmt.Sprintf("    %-10.10s%s\n", command.Name, command.Usage)
+		}
+		return desc
+	}(),
 	Action: listContainers,
 }
 
@@ -109,6 +119,7 @@ func listContainers(context *cli.Context) {
 var startCommand = cli.Command{
 	Name:      "start",
 	Usage:     "start a container",
+	ArgsUsage: "ID BundlePath",
 	Flags: []cli.Flag{
 		cli.StringFlag{
 			Name:  "checkpoint,c",