Add windows spec generation

Signed-off-by: Michael Crosby <crosbymichael@gmail.com>

spec_unix.go

@@ -185,8 +185,10 @@ func WithHostNamespace(ns specs.LinuxNamespaceType) SpecOpts {
 
 func WithImage(ctx context.Context, i Image) SpecOpts {
 	return func(s *specs.Spec) error {
-		image := i.(*image)
+		var (
-		store := image.client.ContentStore()
+			image = i.(*image)
+			store = image.client.ContentStore()
+		)
 		ic, err := image.i.Config(ctx, store)
 		if err != nil {
 			return err

spec_windows.go

@@ -0,0 +1,79 @@
+package containerd
+
+import (
+	"context"
+	"encoding/json"
+	"fmt"
+	"runtime"
+
+	"github.com/containerd/containerd/images"
+	"github.com/opencontainers/image-spec/specs-go/v1"
+	specs "github.com/opencontainers/runtime-spec/specs-go"
+)
+
+const pipeRoot = `\\.\pipe`
+
+func createDefaultSpec() (*specs.Spec, error) {
+	return &specs.Spec{
+		Version: specs.Version,
+		Platform: specs.Platform{
+			OS:   runtime.GOOS,
+			Arch: runtime.GOARCH,
+		},
+		Root: specs.Root{},
+		Process: specs.Process{
+			Env: config.Env,
+			ConsoleSize: specs.Box{
+				Width:  80,
+				Height: 20,
+			},
+		},
+	}, nil
+}
+
+func WithImage(ctx context.Context, i Image) SpecOpts {
+	return func(s *specs.Spec) error {
+		var (
+			image = i.(*image)
+			store = image.client.ContentStore()
+		)
+		ic, err := image.i.Config(ctx, store)
+		if err != nil {
+			return err
+		}
+		var (
+			ociimage v1.Image
+			config   v1.ImageConfig
+		)
+		switch ic.MediaType {
+		case v1.MediaTypeImageConfig, images.MediaTypeDockerSchema2Config:
+			r, err := store.Reader(ctx, ic.Digest)
+			if err != nil {
+				return err
+			}
+			if err := json.NewDecoder(r).Decode(&ociimage); err != nil {
+				r.Close()
+				return err
+			}
+			r.Close()
+			config = ociimage.Config
+		default:
+			return fmt.Errorf("unknown image config media type %s", ic.MediaType)
+		}
+		s.Process.Env = config.Env
+		s.Process.Args = append(config.Entrypoint, config.Cmd...)
+		s.Process.User = specs.User{
+			Username: config.User,
+		}
+		return nil
+	}
+}
+
+func WithTTY(width, height int) SpecOpts {
+	func(s *specs.Spec) error {
+		s.Process.Terminal = true
+		s.Process.ConsoleSize.Width = width
+		s.Process.ConsoleSize.Height = height
+		return nil
+	}
+}