add pkg remote-tag option to tag descriptors remotely without pulling and pushing

Signed-off-by: Avi Deitcher <avi@deitcher.net>

src/cmd/linuxkit/pkg.go

@@ -75,6 +75,7 @@ func pkgCmd() *cobra.Command {
 	cmd.AddCommand(pkgPushCmd())
 	cmd.AddCommand(pkgShowTagCmd())
 	cmd.AddCommand(pkgManifestCmd())
+	cmd.AddCommand(pkgRemoteTagCmd())
 
 	// These override fields in pkgInfo default below, bools are in both forms to allow user overrides in either direction.
 	// These will apply to all packages built.

src/cmd/linuxkit/pkg_remotetag.go

@@ -0,0 +1,65 @@
+package main
+
+import (
+	"fmt"
+
+	"github.com/google/go-containerregistry/pkg/authn"
+	namepkg "github.com/google/go-containerregistry/pkg/name"
+	"github.com/google/go-containerregistry/pkg/v1/remote"
+	"github.com/linuxkit/linuxkit/src/cmd/linuxkit/util"
+	log "github.com/sirupsen/logrus"
+	"github.com/spf13/cobra"
+)
+
+func pkgRemoteTagCmd() *cobra.Command {
+	var release string
+	cmd := &cobra.Command{
+		Use:   "remote-tag",
+		Short: "tag a package in a remote registry with another tag",
+		Long: `Tag a package in a remote registry with another tag, without downloading or pulling.
+		Will simply tag using the identical descriptor.
+		First argument is "from" tag, second is "to" tag.
+`,
+		Args: cobra.ExactArgs(2),
+		RunE: func(cmd *cobra.Command, args []string) error {
+			from := args[0]
+			to := args[1]
+			remoteOptions := []remote.Option{remote.WithAuthFromKeychain(authn.DefaultKeychain)}
+
+			fromFullname := util.ReferenceExpand(from, util.ReferenceWithTag())
+			toFullname := util.ReferenceExpand(to, util.ReferenceWithTag())
+			fromRef, err := namepkg.ParseReference(fromFullname)
+			if err != nil {
+				return err
+			}
+			toRef, err := namepkg.ParseReference(toFullname)
+			if err != nil {
+				return err
+			}
+			fromDesc, err := remote.Get(fromRef, remoteOptions...)
+			if err != nil {
+				return fmt.Errorf("error getting manifest for from image %s: %v", fromFullname, err)
+			}
+			toDesc, err := remote.Get(toRef, remoteOptions...)
+			if err == nil {
+				if toDesc.Digest == fromDesc.Digest {
+					log.Infof("image %s already exists in the registry, identical to %s, skipping", toFullname, fromFullname)
+					return nil
+				}
+				log.Infof("image %s already exists in the registry, but is different from %s, overwriting", toFullname, fromFullname)
+			}
+			toTag, err := namepkg.NewTag(toFullname)
+			if err != nil {
+				return err
+			}
+			if err := remote.Tag(toTag, fromDesc, remoteOptions...); err != nil {
+				return fmt.Errorf("error tagging image %s as %s: %v", fromFullname, toFullname, err)
+			}
+
+			return nil
+		},
+	}
+	cmd.Flags().StringVar(&release, "release", "", "Release the given version")
+
+	return cmd
+}