feat: command to list repositories in a remote registry

cmd/oras/main.go

@@ -5,6 +5,7 @@ import (
 
 	"github.com/spf13/cobra"
 	"oras.land/oras/cmd/oras/manifest"
+	"oras.land/oras/cmd/oras/repository"
 )
 
 func main() {
@@ -22,6 +23,7 @@ func main() {
 		copyCmd(),
 		attachCmd(),
 		manifest.Cmd(),
+		repository.Cmd(),
 	)
 	if err := cmd.Execute(); err != nil {
 		os.Exit(1)

cmd/oras/repository/cmd.go

@@ -0,0 +1,30 @@
+/*
+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 repository
+
+import (
+	"github.com/spf13/cobra"
+)
+
+func Cmd() *cobra.Command {
+	cmd := &cobra.Command{
+		Use:   "repository [command]",
+		Short: "[Preview] Repository operations",
+	}
+
+	cmd.AddCommand(
+		listCmd(),
+	)
+	return cmd
+}

cmd/oras/repository/list.go

@@ -0,0 +1,76 @@
+/*
+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 repository
+
+import (
+	"fmt"
+
+	"github.com/spf13/cobra"
+	"oras.land/oras/cmd/oras/internal/option"
+)
+
+type repositoryOptions struct {
+	option.Remote
+	option.Common
+	hostname string
+	last     string
+}
+
+func listCmd() *cobra.Command {
+	var opts repositoryOptions
+	cmd := &cobra.Command{
+		Use: "list REGISTRY [flags]",
+
+		Short: "[Preview] List the repositories under the registry",
+		Long: `[Preview] List the repositories under the registry
+
+** This command is in preview and under development. **
+
+Example - List the repositories under the registry:
+  oras repository list localhost:5000
+
+Example - List the repositories under the registry that include values lexically after last:
+  oras repository list localhost:5000 --last "last_repo"
+`,
+		Args:    cobra.ExactArgs(1),
+		Aliases: []string{"ls"},
+		RunE: func(cmd *cobra.Command, args []string) error {
+			opts.hostname = args[0]
+			return listRepository(opts)
+		},
+	}
+
+	option.ApplyFlags(&opts, cmd.Flags())
+	cmd.Flags().StringVar(&opts.last, "last", "", "start after the repository specified by `last`")
+	return cmd
+}
+
+func listRepository(opts repositoryOptions) error {
+	ctx, _ := opts.SetLoggerLevel()
+	reg, err := opts.Remote.NewRegistry(opts.hostname, opts.Common)
+	if err != nil {
+		return err
+	}
+	if listErr := reg.Repositories(ctx, opts.last, func(repos []string) error {
+		for _, repo := range repos {
+			fmt.Println(repo)
+		}
+		return nil
+	}); listErr != nil {
+		return listErr
+	}
+	return nil
+}