Add support for --image-refs

This change adds a new `--image-refs=FILE` flag that can be used to
direct `ko` to write a file containing a `\n` delimited list of published
references.  In the common case, this will contain the list of digest
references, but if flags directing the use of tags are present this
will reflect the style of reference requested.

pkg/commands/options/publish.go

@@ -59,6 +59,8 @@ type PublishOptions struct {
 	OCILayoutPath string
 	TarballFile   string
 
+	ImageRefsFile string
+
 	// PreserveImportPaths preserves the full import path after KO_DOCKER_REPO.
 	PreserveImportPaths bool
 	// BaseImportPaths uses the base path without MD5 hash after KO_DOCKER_REPO.
@@ -93,6 +95,9 @@ func AddPublishArg(cmd *cobra.Command, po *PublishOptions) {
 	cmd.Flags().StringVar(&po.OCILayoutPath, "oci-layout-path", "", "Path to save the OCI image layout of the built images")
 	cmd.Flags().StringVar(&po.TarballFile, "tarball", "", "File to save images tarballs")
 
+	cmd.Flags().StringVar(&po.ImageRefsFile, "image-refs", "",
+		"Path to file where a list of the published image references will be written.")
+
 	cmd.Flags().BoolVarP(&po.PreserveImportPaths, "preserve-import-paths", "P", po.PreserveImportPaths,
 		"Whether to preserve the full import path after KO_DOCKER_REPO.")
 	cmd.Flags().BoolVarP(&po.BaseImportPaths, "base-import-paths", "B", po.BaseImportPaths,

pkg/commands/resolver.go

@@ -215,7 +215,8 @@ func makePublisher(po *options.PublishOptions) (publish.Interface, error) {
 				publish.WithNamer(namer),
 				publish.WithTags(po.Tags),
 				publish.WithTagOnly(po.TagOnly),
-				publish.Insecure(po.InsecureRegistry))
+				publish.Insecure(po.InsecureRegistry),
+			)
 			if err != nil {
 				return nil, err
 			}
@@ -237,6 +238,17 @@ func makePublisher(po *options.PublishOptions) (publish.Interface, error) {
 		return nil, err
 	}
 
+	if po.ImageRefsFile != "" {
+		f, err := os.OpenFile(po.ImageRefsFile, os.O_RDWR|os.O_CREATE, 0600)
+		if err != nil {
+			return nil, err
+		}
+		innerPublisher, err = publish.NewRecorder(innerPublisher, f)
+		if err != nil {
+			return nil, err
+		}
+	}
+
 	// Wrap publisher in a memoizing publisher implementation.
 	return publish.NewCaching(innerPublisher)
 }

pkg/publish/recorder.go

@@ -0,0 +1,65 @@
+// 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 publish
+
+import (
+	"context"
+	"io"
+
+	"github.com/google/go-containerregistry/pkg/name"
+	"github.com/google/ko/pkg/build"
+)
+
+// recorder wraps a publisher implementation in a layer that recordes the published
+// references to an io.Writer.
+type recorder struct {
+	inner Interface
+	wc    io.Writer
+}
+
+// recorder implements Interface
+var _ Interface = (*recorder)(nil)
+
+// NewRecorder wraps the provided publish.Interface in an implementation that
+// records publish results to an io.Writer.
+func NewRecorder(inner Interface, wc io.Writer) (Interface, error) {
+	return &recorder{
+		inner: inner,
+		wc:    wc,
+	}, nil
+}
+
+// Publish implements Interface
+func (r *recorder) Publish(ctx context.Context, br build.Result, ref string) (name.Reference, error) {
+	result, err := r.inner.Publish(ctx, br, ref)
+	if err != nil {
+		return nil, err
+	}
+	if _, err := r.wc.Write([]byte(result.String() + "\n")); err != nil {
+		return nil, err
+	}
+	return result, nil
+}
+
+// Close implements Interface
+func (r *recorder) Close() error {
+	if err := r.inner.Close(); err != nil {
+		return err
+	}
+	if c, ok := r.wc.(io.Closer); ok {
+		return c.Close()
+	}
+	return nil
+}

pkg/publish/recorder_test.go

@@ -0,0 +1,73 @@
+// 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 publish
+
+import (
+	"bytes"
+	"context"
+	"fmt"
+	"testing"
+
+	"github.com/google/go-containerregistry/pkg/name"
+	"github.com/google/ko/pkg/build"
+)
+
+type cbPublish struct {
+	cb func(context.Context, build.Result, string) (name.Reference, error)
+}
+
+var _ Interface = (*slowpublish)(nil)
+
+func (sp *cbPublish) Publish(ctx context.Context, br build.Result, ref string) (name.Reference, error) {
+	return sp.cb(ctx, br, ref)
+}
+
+func (sp *cbPublish) Close() error {
+	return nil
+}
+
+func TestRecorder(t *testing.T) {
+
+	num := 0
+	inner := &cbPublish{cb: func(c context.Context, b build.Result, s string) (name.Reference, error) {
+		num++
+		return name.ParseReference(fmt.Sprintf("ubuntu:%d", num))
+	}}
+
+	buf := bytes.NewBuffer(nil)
+
+	recorder, err := NewRecorder(inner, buf)
+	if err != nil {
+		t.Fatalf("NewRecorder() = %v", err)
+	}
+
+	if _, err := recorder.Publish(context.Background(), nil, ""); err != nil {
+		t.Errorf("recorder.Publish() = %v", err)
+	}
+	if _, err := recorder.Publish(context.Background(), nil, ""); err != nil {
+		t.Errorf("recorder.Publish() = %v", err)
+	}
+	if _, err := recorder.Publish(context.Background(), nil, ""); err != nil {
+		t.Errorf("recorder.Publish() = %v", err)
+	}
+	if err := recorder.Close(); err != nil {
+		t.Errorf("recorder.Close() = %v", err)
+	}
+
+	want, got := "ubuntu:1\nubuntu:2\nubuntu:3\n", buf.String()
+	if got != want {
+		t.Errorf("buf.String() = %s, wanted %s", got, want)
+	}
+}