Attempt to preserve old Docker image format

internal/cmd/dockerpush/main.go

@@ -39,14 +39,12 @@ func run(basedir string, dockerOrg string) error {
 		return nil // nothing to push
 	}
 	for _, includedPlugin := range includedPlugins {
-		output, err := docker.Push(ctx, includedPlugin, dockerOrg)
-		if err != nil {
+		if err := docker.Push(ctx, includedPlugin, dockerOrg); err != nil {
 			log.Printf(
-				"docker push of plugin %s:%s failed with err %v:\noutput:\n%s",
+				"docker push of plugin %s:%s failed: %v",
 				includedPlugin.Name,
 				includedPlugin.PluginVersion,
 				err,
-				string(output),
 			)
 			return err
 		}

internal/docker/push.go

@@ -2,20 +2,50 @@ package docker
 
 import (
 	"context"
+	"errors"
+	"fmt"
+	"os"
 	"os/exec"
 
+	"github.com/google/go-containerregistry/pkg/authn"
+	"github.com/google/go-containerregistry/pkg/name"
+	"github.com/google/go-containerregistry/pkg/v1/remote"
+	"github.com/google/go-containerregistry/pkg/v1/tarball"
+
 	"github.com/bufbuild/plugins/internal/plugin"
 )
 
 // Push pushes a docker image for the given plugin to the Docker organization.
 // It assumes it has already been built in a previous step.
-func Push(ctx context.Context, plugin *plugin.Plugin, dockerOrg string) ([]byte, error) {
-	imageName := ImageName(plugin, dockerOrg)
-	cmd := exec.CommandContext(
-		ctx,
-		"docker",
-		"push",
-		imageName,
-	)
-	return cmd.CombinedOutput()
+//
+// Images are saved from the local Docker daemon via "docker save" and pushed
+// using go-containerregistry to preserve Docker distribution manifest v2 format.
+func Push(ctx context.Context, pluginToPush *plugin.Plugin, dockerOrg string) (retErr error) {
+	imageName := ImageName(pluginToPush, dockerOrg)
+	tmpFile, err := os.CreateTemp("", "plugin-image-*.tar")
+	if err != nil {
+		return fmt.Errorf("create temp file: %w", err)
+	}
+	defer func() {
+		retErr = errors.Join(retErr, os.Remove(tmpFile.Name()))
+	}()
+	if err := tmpFile.Close(); err != nil {
+		return fmt.Errorf("close temp file: %w", err)
+	}
+	cmd := exec.CommandContext(ctx, "docker", "save", imageName, "-o", tmpFile.Name())
+	if output, err := cmd.CombinedOutput(); err != nil {
+		return fmt.Errorf("docker save %q: %w\noutput: %s", imageName, err, output)
+	}
+	image, err := tarball.ImageFromPath(tmpFile.Name(), nil)
+	if err != nil {
+		return fmt.Errorf("load image from tarball: %w", err)
+	}
+	tag, err := name.NewTag(imageName)
+	if err != nil {
+		return fmt.Errorf("parse image reference %q: %w", imageName, err)
+	}
+	if err := remote.Write(tag, image, remote.WithAuthFromKeychain(authn.DefaultKeychain), remote.WithContext(ctx)); err != nil {
+		return fmt.Errorf("push image %q: %w", imageName, err)
+	}
+	return nil
 }