validation/util/container: Use --bundle (and stop requiring BundleDir)

Address a previous TODO.  And now that we are using --bundle, we no
longer need to set cmd.Dir.  The TODO mentions a lack of runc support,
but runc supports --bundle since opencontainers/runc@3fe7d7f3 (Add
create and start command for container lifecycle, 2016-05-13,
opencontainers/runc#827).

validation/util/container.go

@@ -2,7 +2,6 @@ package util
 
 import (
 	"encoding/json"
-	"errors"
 	"fmt"
 	"io"
 	"io/ioutil"
@@ -11,6 +10,7 @@ import (
 	"path/filepath"
 
 	rspecs "github.com/opencontainers/runtime-spec/specs-go"
+	"github.com/opencontainers/runtime-tools/clierror"
 	"github.com/opencontainers/runtime-tools/generate"
 	"github.com/satori/go.uuid"
 )
@@ -30,19 +30,26 @@ func NewRuntime(runtimeCommand string, bundleDir string) (Runtime, error) {
 	var err error
 	r.RuntimeCommand, err = exec.LookPath(runtimeCommand)
 	if err != nil {
-		return Runtime{}, err
+		return Runtime{}, clierror.NewError(clierror.Executable, err, "1.0.0")
 	}
 
 	r.BundleDir = bundleDir
 	return r, err
 }
 
-// SetConfig creates a 'config.json' by the generator
-func (r *Runtime) SetConfig(g *generate.Generator) error {
+// bundleDir returns the bundle directory.  Generally this is
+// BundleDir, but when BundleDir is the empty string, it falls back to
+// ., as specified in the CLI spec.
+func (r *Runtime) bundleDir() (bundleDir string) {
 	if r.BundleDir == "" {
-		return errors.New("Please set the bundle directory first")
+		return "."
 	}
-	return g.SaveToFile(filepath.Join(r.BundleDir, "config.json"), generate.ExportOptions{})
+	return r.BundleDir
+}
+
+// SetConfig creates a 'config.json' by the generator
+func (r *Runtime) SetConfig(g *generate.Generator) error {
+	return g.SaveToFile(filepath.Join(r.bundleDir(), "config.json"), generate.ExportOptions{})
 }
 
 // SetID sets the container ID
@@ -58,19 +65,17 @@ func (r *Runtime) Create() (stderr []byte, err error) {
 		args = append(args, r.ID)
 	}
 
-	// TODO: following the spec, we need define the bundle, but 'runc' does not..
-	//	if r.BundleDir != "" {
-	//		args = append(args, r.BundleDir)
-	//	}
+	if r.BundleDir != "" {
+		args = append(args, "--bundle", r.BundleDir)
+	}
 	cmd := exec.Command(r.RuntimeCommand, args...)
-	cmd.Dir = r.BundleDir
 	id := uuid.NewV4().String()
-	r.stdout, err = os.OpenFile(filepath.Join(r.BundleDir, fmt.Sprintf("stdout-%s", id)), os.O_CREATE|os.O_EXCL|os.O_RDWR, 0600)
+	r.stdout, err = os.OpenFile(filepath.Join(r.bundleDir(), fmt.Sprintf("stdout-%s", id)), os.O_CREATE|os.O_EXCL|os.O_RDWR, 0600)
 	if err != nil {
 		return []byte(""), err
 	}
 	cmd.Stdout = r.stdout
-	r.stderr, err = os.OpenFile(filepath.Join(r.BundleDir, fmt.Sprintf("stderr-%s", id)), os.O_CREATE|os.O_EXCL|os.O_RDWR, 0600)
+	r.stderr, err = os.OpenFile(filepath.Join(r.bundleDir(), fmt.Sprintf("stderr-%s", id)), os.O_CREATE|os.O_EXCL|os.O_RDWR, 0600)
 	if err != nil {
 		return []byte(""), err
 	}
@@ -161,7 +166,7 @@ func (r *Runtime) Clean(removeBundle bool, forceRemoveBundle bool) error {
 	err := r.Delete()
 
 	if removeBundle && (err == nil || forceRemoveBundle) {
-		err2 := os.RemoveAll(r.BundleDir)
+		err2 := os.RemoveAll(r.bundleDir())
 		if err2 != nil && err == nil {
 			err = err2
 		}