adds support for the /v2/_catalog API

cmd/crane/cmd/catalog.go

@@ -0,0 +1,45 @@
+// Copyright 2018 Google LLC All Rights Reserved.
+//
+// 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 cmd
+
+import (
+	"fmt"
+	"log"
+
+	"github.com/google/go-containerregistry/pkg/crane"
+	"github.com/spf13/cobra"
+)
+
+func init() { Root.AddCommand(NewCmdGetCatalog()) }
+
+// NewCmdGetCatalog creates a new cobra.Command for the repos subcommand.
+func NewCmdGetCatalog() *cobra.Command {
+	return &cobra.Command{
+		Use:   "catalog",
+		Short: "List the repos in a registry",
+		Args:  cobra.ExactArgs(1),
+		Run: func(_ *cobra.Command, args []string) {
+			reg := args[0]
+			repos, err := crane.GetCatalog(reg)
+			if err != nil {
+				log.Fatalf("reading repos for %s: %v", reg, err)
+			}
+
+			for _, repo := range repos {
+				fmt.Println(repo)
+			}
+		},
+	}
+}

pkg/crane/catalog.go

@@ -0,0 +1,51 @@
+// Copyright 2018 Google LLC All Rights Reserved.
+//
+// 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 crane
+
+import (
+	"github.com/google/go-containerregistry/pkg/authn"
+	"github.com/google/go-containerregistry/pkg/name"
+	"github.com/google/go-containerregistry/pkg/v1/remote"
+)
+
+// GetCatalog returns the repositories in a registry's catalog
+func GetCatalog(src string) (res []string, err error) {
+	reg, err := name.NewRegistry(src)
+	if err != nil {
+		return nil, err
+	}
+
+	n := 100
+	last := ""
+	for {
+
+		page, err := remote.GetCatalogPage(reg, last, n, remote.WithAuthFromKeychain(authn.DefaultKeychain))
+		if err != nil {
+			return nil, err
+		}
+
+		if len(page) > 0 {
+			last = page[len(page)-1]
+			res = append(res, page...)
+		}
+
+		if len(page) < n {
+			break
+		}
+
+	}
+
+	return res, nil
+}