feat: enable tagging manifests (#519)

Signed-off-by: Jun <[email protected]>

cmd/oras/main.go

@@ -6,6 +6,7 @@ import (
 	"github.com/spf13/cobra"
 	"oras.land/oras/cmd/oras/manifest"
 	"oras.land/oras/cmd/oras/repository"
+	"oras.land/oras/cmd/oras/tag"
 )
 
 func main() {
@@ -23,6 +24,7 @@ func main() {
 		copyCmd(),
 		attachCmd(),
 		manifest.Cmd(),
+		tag.TagCmd(),
 		repository.Cmd(),
 	)
 	if err := cmd.Execute(); err != nil {

cmd/oras/tag/tag.go

@@ -0,0 +1,74 @@
+/*
+Copyright The ORAS Authors.
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package tag
+
+import (
+	"github.com/spf13/cobra"
+	"oras.land/oras-go/v2"
+	"oras.land/oras/cmd/oras/internal/errors"
+	"oras.land/oras/cmd/oras/internal/option"
+)
+
+type tagOptions struct {
+	option.Common
+	option.Remote
+
+	srcRef    string
+	targetRef string
+}
+
+func TagCmd() *cobra.Command {
+	var opts tagOptions
+	cmd := &cobra.Command{
+		Use:   "tag name<:tag|@digest> new_tag",
+		Short: "[Preview] tag a manifest in the remote registry",
+		Long: `[Preview] tag a manifest in the remote registry
+
+** This command is in preview and under development. **
+
+Example - Tag the manifest 'v1.0.1' in 'locahost:5000/hello' to 'v1.0.2':
+  oras tag localhost:5000/hello:v1.0.1 v1.0.2
+
+Example - Tag the manifest with digest sha256:9463e0d192846bc994279417b50114606712d516aab45f4d8b31cbc6e46aad71 to 'v1.0.3'
+  oras tag localhost:5000/hello@sha256:9463e0d192846bc994279417b50114606712d516aab45f4d8b31cbc6e46aad71 v1.0.3
+`,
+		Args: cobra.ExactArgs(2),
+		PreRunE: func(cmd *cobra.Command, args []string) error {
+			return opts.ReadPassword()
+		},
+		RunE: func(_ *cobra.Command, args []string) error {
+			opts.srcRef = args[0]
+			opts.targetRef = args[1]
+			return tagManifest(opts)
+		},
+	}
+	option.ApplyFlags(&opts, cmd.Flags())
+	return cmd
+}
+
+func tagManifest(opts tagOptions) error {
+	ctx, _ := opts.SetLoggerLevel()
+	repo, err := opts.NewRepository(opts.srcRef, opts.Common)
+	if err != nil {
+		return err
+	}
+
+	if repo.Reference.Reference == "" {
+		return errors.NewErrInvalidReference(repo.Reference)
+	}
+
+	return oras.Tag(ctx, repo, opts.srcRef, opts.targetRef)
+}