Merge pull request #1247 from tonistiigi/dangling-naming

exporter: add canonical and dangling image naming

README.md

@@ -45,7 +45,7 @@ You don't need to read this document unless you want to use the full-featured st
     - [Building a Dockerfile using external frontend:](#building-a-dockerfile-using-external-frontend)
     - [Building a Dockerfile with experimental features like `RUN --mount=type=(bind|cache|tmpfs|secret|ssh)`](#building-a-dockerfile-with-experimental-features-like-run---mounttypebindcachetmpfssecretssh)
   - [Output](#output)
-    - [Registry](#registry)
+    - [Image/Registry](#imageregistry)
     - [Local directory](#local-directory)
     - [Docker tarball](#docker-tarball)
     - [OCI tarball](#oci-tarball)
@@ -199,7 +199,7 @@ See [`frontend/dockerfile/docs/experimental.md`](frontend/dockerfile/docs/experi
 
 By default, the build result and intermediate cache will only remain internally in BuildKit. An output needs to be specified to retrieve the result.
 
-#### Registry
+#### Image/Registry
 
 ```bash
 buildctl build ... --output type=image,name=docker.io/username/image,push=true
@@ -215,6 +215,17 @@ buildctl build ...\
   --import-cache type=registry,ref=docker.io/username/image
 ```
 
+Keys supported by image output:
+* `name=[value]`: image name
+* `push=true`: push after creating the image
+* `push-by-digest=true`: push unnamed image
+* `registry.insecure=true`: push to insecure HTTP registry
+* `oci-mediatypes=true`: use OCI mediatypes in configuration JSON instead of Docker's
+* `unpack=true`: unpack image after creation (for use with containerd)
+* `dangling-name-prefix=[value]`: name image with `prefix@<digest>` , used for anonymous images
+* `name-canonical=true`: add additional canonical name `name@<digest>`
+
+
 If credentials are required, `buildctl` will attempt to read Docker configuration file `$DOCKER_CONFIG/config.json`.
 `$DOCKER_CONFIG` defaults to `~/.docker`.
 

exporter/containerimage/export.go

@@ -31,6 +31,8 @@ const (
 	keyPushByDigest   = "push-by-digest"
 	keyInsecure       = "registry.insecure"
 	keyUnpack         = "unpack"
+	keyDanglingPrefix = "dangling-name-prefix"
+	keyNameCanonical  = "name-canonical"
 	ociTypes          = "oci-mediatypes"
 )
 
@@ -111,6 +113,18 @@ func (e *imageExporter) Resolve(ctx context.Context, opt map[string]string) (exp
 				return nil, errors.Wrapf(err, "non-bool value specified for %s", k)
 			}
 			i.ociTypes = b
+		case keyDanglingPrefix:
+			i.danglingPrefix = v
+		case keyNameCanonical:
+			if v == "" {
+				i.nameCanonical = true
+				continue
+			}
+			b, err := strconv.ParseBool(v)
+			if err != nil {
+				return nil, errors.Wrapf(err, "non-bool value specified for %s", k)
+			}
+			i.nameCanonical = b
 		default:
 			if i.meta == nil {
 				i.meta = make(map[string][]byte)
@@ -129,6 +143,8 @@ type imageExporterInstance struct {
 	unpack         bool
 	insecure       bool
 	ociTypes       bool
+	nameCanonical  bool
+	danglingPrefix string
 	meta           map[string][]byte
 }
 
@@ -165,17 +181,27 @@ func (e *imageExporterInstance) Export(ctx context.Context, src exporter.Source)
 		e.targetName = string(n)
 	}
 
+	nameCanonical := e.nameCanonical
+	if e.targetName == "" && e.danglingPrefix != "" {
+		e.targetName = e.danglingPrefix + "@" + desc.Digest.String()
+		nameCanonical = false
+	}
+
 	if e.targetName != "" {
 		targetNames := strings.Split(e.targetName, ",")
 		for _, targetName := range targetNames {
 			if e.opt.Images != nil {
 				tagDone := oneOffProgress(ctx, "naming to "+targetName)
 				img := images.Image{
-					Name:      targetName,
 					Target:    *desc,
 					CreatedAt: time.Now(),
 				}
-
+				sfx := []string{""}
+				if nameCanonical {
+					sfx = append(sfx, "@"+desc.Digest.String())
+				}
+				for _, sfx := range sfx {
+					img.Name = targetName + sfx
 					if _, err := e.opt.Images.Update(ctx, img); err != nil {
 						if !errdefs.IsNotFound(err) {
 							return nil, tagDone(err)
@@ -185,6 +211,7 @@ func (e *imageExporterInstance) Export(ctx context.Context, src exporter.Source)
 							return nil, tagDone(err)
 						}
 					}
+				}
 				tagDone(nil)
 
 				if e.unpack {