Add push object

Split resolver to only return a name with separate methods
for getting a fetcher and pusher. Add implementation for
push.

Signed-off-by: Derek McGowan <derek@mcgstyle.net>

cmd/dist/pushobject.go

@@ -0,0 +1,75 @@
+package main
+
+import (
+	"fmt"
+
+	"github.com/containerd/containerd/log"
+	digest "github.com/opencontainers/go-digest"
+	ocispec "github.com/opencontainers/image-spec/specs-go/v1"
+	"github.com/urfave/cli"
+)
+
+var pushObjectCommand = cli.Command{
+	Name:        "push-object",
+	Usage:       "pushes an object to a remote",
+	ArgsUsage:   "[flags] <remote> <object> <type>",
+	Description: `Push objects by identifier to a remote.`,
+	Flags:       registryFlags,
+	Action: func(clicontext *cli.Context) error {
+		var (
+			ref    = clicontext.Args().Get(0)
+			object = clicontext.Args().Get(1)
+			media  = clicontext.Args().Get(2)
+		)
+		dgst, err := digest.Parse(object)
+		if err != nil {
+			return err
+		}
+
+		ctx, cancel := appContext()
+		defer cancel()
+
+		resolver, err := getResolver(ctx, clicontext)
+		if err != nil {
+			return err
+		}
+
+		ctx = log.WithLogger(ctx, log.G(ctx).WithField("ref", ref))
+
+		log.G(ctx).Infof("resolving")
+		pusher, err := resolver.Pusher(ctx, ref)
+		if err != nil {
+			return err
+		}
+
+		cs, err := resolveContentStore(clicontext)
+		if err != nil {
+			return err
+		}
+
+		info, err := cs.Info(ctx, dgst)
+		if err != nil {
+			return err
+		}
+		desc := ocispec.Descriptor{
+			MediaType: media,
+			Digest:    dgst,
+			Size:      info.Size,
+		}
+
+		rc, err := cs.Reader(ctx, dgst)
+		if err != nil {
+			return err
+		}
+		defer rc.Close()
+
+		// TODO: Progress reader
+		if err = pusher.Push(ctx, desc, rc); err != nil {
+			return err
+		}
+
+		fmt.Printf("Pushed %s %s\n", desc.Digest, desc.MediaType)
+
+		return nil
+	},
+}