Add list artifacts command

Signed-off-by: Stefan Prodan <stefan.prodan@gmail.com>

internal/oci/list.go

@@ -0,0 +1,70 @@
+/*
+Copyright 2022 The Flux 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 oci
+
+import (
+	"bytes"
+	"context"
+	"fmt"
+	"sort"
+	"strings"
+
+	"github.com/google/go-containerregistry/pkg/crane"
+	gcrv1 "github.com/google/go-containerregistry/pkg/v1"
+)
+
+// List fetches the tags and their manifests for a given OCI repository.
+func List(ctx context.Context, url string) ([]Metadata, error) {
+	metas := make([]Metadata, 0)
+	tags, err := crane.ListTags(url, craneOptions(ctx)...)
+	if err != nil {
+		return nil, fmt.Errorf("listing tags failed: %w", err)
+	}
+
+	sort.Slice(tags, func(i, j int) bool { return tags[i] > tags[j] })
+
+	for _, tag := range tags {
+		// exclude cosign signatures
+		if strings.HasSuffix(tag, ".sig") {
+			continue
+		}
+
+		meta := Metadata{
+			URL: fmt.Sprintf("%s:%s", url, tag),
+		}
+
+		manifestJSON, err := crane.Manifest(meta.URL, craneOptions(ctx)...)
+		if err != nil {
+			return nil, fmt.Errorf("fetching manifest failed: %w", err)
+		}
+
+		manifest, err := gcrv1.ParseManifest(bytes.NewReader(manifestJSON))
+		if err != nil {
+			return nil, fmt.Errorf("parsing manifest failed: %w", err)
+		}
+
+		meta.Digest = manifest.Config.Digest.String()
+		if m, err := MetadataFromAnnotations(manifest.Annotations); err == nil {
+			meta.Revision = m.Revision
+			meta.Source = m.Source
+		}
+
+		metas = append(metas, meta)
+	}
+
+	return metas, nil
+}

internal/oci/meta.go

@@ -29,6 +29,7 @@ type Metadata struct {
 	Source   string `json:"source_url"`
 	Revision string `json:"source_revision"`
 	Digest   string `json:"digest"`
+	URL      string `json:"url"`
 }
 
 func (m *Metadata) ToAnnotations() map[string]string {
@@ -40,7 +41,7 @@ func (m *Metadata) ToAnnotations() map[string]string {
 	return annotations
 }
 
-func GetMetadata(annotations map[string]string) (*Metadata, error) {
+func MetadataFromAnnotations(annotations map[string]string) (*Metadata, error) {
 	source, ok := annotations[SourceAnnotation]
 	if !ok {
 		return nil, fmt.Errorf("'%s' annotation not found", SourceAnnotation)

internal/oci/pull.go

@@ -47,7 +47,7 @@ func Pull(ctx context.Context, url, outDir string) (*Metadata, error) {
 		return nil, fmt.Errorf("parsing manifest failed: %w", err)
 	}
 
-	meta, err := GetMetadata(manifest.Annotations)
+	meta, err := MetadataFromAnnotations(manifest.Annotations)
 	if err != nil {
 		return nil, err
 	}