cmd/skopeo: refactor layers command

Signed-off-by: Antonio Murdaca <runcom@redhat.com>

cmd/skopeo/layers.go

@@ -1,6 +1,11 @@
 package main
 
 import (
+	"io/ioutil"
+	"strings"
+
+	"github.com/containers/image/directory"
+	"github.com/containers/image/image"
 	"github.com/urfave/cli"
 )
 
@@ -9,13 +14,45 @@ var layersCmd = cli.Command{
 	Name:  "layers",
 	Usage: "get images layers",
 	Action: func(c *cli.Context) error {
-		img, err := parseImage(c)
+		rawSource, err := parseImageSource(c, c.Args()[0])
 		if err != nil {
 			return err
 		}
-		if err := img.LayersCommand(c.Args().Tail()...); err != nil {
+		src := image.FromSource(rawSource)
+		layers := c.Args().Tail()
+		if len(layers) == 0 {
+			ls, err := src.LayerDigests()
+			if err != nil {
+				return err
+			}
+			layers = ls
+		}
+		tmpDir, err := ioutil.TempDir(".", "layers-")
+		if err != nil {
 			return err
 		}
+		dest := directory.NewDirImageDestination(tmpDir)
+		manifest, err := src.Manifest()
+		if err != nil {
+			return err
+		}
+		if err := dest.PutManifest(manifest); err != nil {
+			return err
+		}
+		for _, l := range layers {
+			if !strings.HasPrefix(l, "sha256:") {
+				l = "sha256:" + l
+			}
+			r, _, err := rawSource.GetBlob(l)
+			if err != nil {
+				return err
+			}
+			if err := dest.PutBlob(l, r); err != nil {
+				r.Close()
+				return err
+			}
+			r.Close()
+		}
 		return nil
 	},
 }