execProcess: move some code to newProcess

Let's move some code from execProcess to newProcess, fixing the
following few issues:

1. container.State (which does quite a lot) is not needed --
   we only need container.Config here.

2. utils.SearchLabels is not needed when "runc exec --process" is used.

3. Context.String("process") is called twice.

4. It is not very clear from the code why checking for
   len(context.Args()) is performed. Move the check to just before
   Args is used, to make it clear why.

Signed-off-by: Kir Kolyshkin <[email protected]>

Author: kolyshkin

exec.go

@@ -158,19 +158,7 @@ func execProcess(context *cli.Context) (int, error) {
 	if status == libcontainer.Paused && !context.Bool("ignore-paused") {
 		return -1, errors.New("cannot exec in a paused container (use --ignore-paused to override)")
 	}
-	path := context.String("process")
-	if path == "" && len(context.Args()) == 1 {
-		return -1, errors.New("process args cannot be empty")
-	}
-	state, err := container.State()
-	if err != nil {
-		return -1, err
-	}
-	bundle, ok := utils.SearchLabels(state.Config.Labels, "bundle")
-	if !ok {
-		return -1, errors.New("bundle not found in labels")
-	}
-	p, err := getProcess(context, bundle)
+	p, err := getProcess(context, container)
 	if err != nil {
 		return -1, err
 	}
@@ -196,7 +184,7 @@ func execProcess(context *cli.Context) (int, error) {
 	return r.run(p)
 }
 
-func getProcess(context *cli.Context, bundle string) (*specs.Process, error) {
+func getProcess(context *cli.Context, c *libcontainer.Container) (*specs.Process, error) {
 	if path := context.String("process"); path != "" {
 		f, err := os.Open(path)
 		if err != nil {
@@ -209,7 +197,11 @@ func getProcess(context *cli.Context, bundle string) (*specs.Process, error) {
 		}
 		return &p, validateProcessSpec(&p)
 	}
-	// process via cli flags
+	// Process from config.json and CLI flags.
+	bundle, ok := utils.SearchLabels(c.Config().Labels, "bundle")
+	if !ok {
+		return nil, errors.New("bundle not found in labels")
+	}
 	if err := os.Chdir(bundle); err != nil {
 		return nil, err
 	}
@@ -218,7 +210,11 @@ func getProcess(context *cli.Context, bundle string) (*specs.Process, error) {
 		return nil, err
 	}
 	p := spec.Process
-	p.Args = context.Args()[1:]
+	args := context.Args()
+	if len(args) < 2 {
+		return nil, errors.New("exec args cannot be empty")
+	}
+	p.Args = args[1:]
 	// Override the cwd, if passed.
 	if cwd := context.String("cwd"); cwd != "" {
 		p.Cwd = cwd