Add crane-based methods for extraction

- create a new api package to encapsulate image manipulation
- use new api method to calculate delta

Fixes #258
Fixes #204
Fixes #90

pkg/compiler/backend/simpledocker.go

@@ -23,10 +23,13 @@ import (
 	"path/filepath"
 	"strings"
 
+	"github.com/google/go-containerregistry/pkg/name"
+	"github.com/google/go-containerregistry/pkg/v1/daemon"
 	"github.com/mudler/luet/pkg/api/core/types"
 	bus "github.com/mudler/luet/pkg/bus"
 	fileHelper "github.com/mudler/luet/pkg/helpers/file"
 
+	v1 "github.com/google/go-containerregistry/pkg/v1"
 	capi "github.com/mudler/docker-companion/api"
 
 	"github.com/mudler/luet/pkg/helpers"
@@ -144,6 +147,19 @@ func (s *SimpleDocker) Push(opts Options) error {
 	return nil
 }
 
+func (s *SimpleDocker) ImageReference(a string) (v1.Image, error) {
+	ref, err := name.ParseReference(a)
+	if err != nil {
+		return nil, err
+	}
+
+	img, err := daemon.Image(ref)
+	if err != nil {
+		return nil, err
+	}
+	return img, nil
+}
+
 func (s *SimpleDocker) ImageDefinitionToTar(opts Options) error {
 	if err := s.BuildImage(opts); err != nil {
 		return errors.Wrap(err, "Failed building image")

pkg/compiler/backend/simpledocker_test.go

@@ -17,8 +17,6 @@ package backend_test
 
 import (
 	"github.com/mudler/luet/pkg/api/core/types"
-	"github.com/mudler/luet/pkg/api/core/types/artifact"
-	"github.com/mudler/luet/pkg/compiler"
 	. "github.com/mudler/luet/pkg/compiler"
 	"github.com/mudler/luet/pkg/compiler/backend"
 	. "github.com/mudler/luet/pkg/compiler/backend"
@@ -107,35 +105,6 @@ RUN echo bar > /test2`))
 			Expect(b.ExportImage(opts2)).ToNot(HaveOccurred())
 			Expect(fileHelper.Exists(filepath.Join(tmpdir, "output2.tar"))).To(BeTrue())
 
-			artifacts := []artifact.ArtifactNode{{
-				Name: "/luetbuild/LuetDockerfile",
-				Size: 175,
-			}}
-			if os.Getenv("DOCKER_BUILDKIT") == "1" {
-				artifacts = append(artifacts, artifact.ArtifactNode{Name: "/etc/resolv.conf", Size: 0})
-			}
-			artifacts = append(artifacts, artifact.ArtifactNode{Name: "/test", Size: 4})
-			artifacts = append(artifacts, artifact.ArtifactNode{Name: "/test2", Size: 4})
-
-			Expect(compiler.GenerateChanges(ctx, b, opts, opts2)).To(Equal(
-				[]artifact.ArtifactLayer{{
-					FromImage: "luet/base",
-					ToImage:   "test",
-					Diffs: artifact.ArtifactDiffs{
-						Additions: artifacts,
-					},
-				}}))
-
-			opts2 = backend.Options{
-				ImageName:      "test",
-				SourcePath:     tmpdir,
-				DockerFileName: "LuetDockerfile",
-				Destination:    filepath.Join(tmpdir, "output3.tar"),
-			}
-
-			Expect(b.ImageDefinitionToTar(opts2)).ToNot(HaveOccurred())
-			Expect(fileHelper.Exists(filepath.Join(tmpdir, "output3.tar"))).To(BeTrue())
-			Expect(b.ImageExists(opts2.ImageName)).To(BeFalse())
 		})
 
 		It("Detects available images", func() {

pkg/compiler/backend/simpleimg.go

@@ -20,6 +20,8 @@ import (
 	"os/exec"
 	"strings"
 
+	"github.com/google/go-containerregistry/pkg/crane"
+	v1 "github.com/google/go-containerregistry/pkg/v1"
 	"github.com/mudler/luet/pkg/api/core/types"
 	bus "github.com/mudler/luet/pkg/bus"
 
@@ -70,6 +72,29 @@ func (s *SimpleImg) RemoveImage(opts Options) error {
 	return nil
 }
 
+func (s *SimpleImg) ImageReference(a string) (v1.Image, error) {
+
+	f, err := s.ctx.Config.GetSystem().TempFile("snapshot")
+	if err != nil {
+		return nil, err
+	}
+	buildarg := []string{"save", a, "-o", f.Name()}
+	s.ctx.Spinner()
+	defer s.ctx.SpinnerStop()
+
+	out, err := exec.Command("img", buildarg...).CombinedOutput()
+	if err != nil {
+		return nil, errors.Wrap(err, "Failed saving image: "+string(out))
+	}
+
+	img, err := crane.Load(f.Name())
+	if err != nil {
+		return nil, err
+	}
+
+	return img, nil
+}
+
 func (s *SimpleImg) DownloadImage(opts Options) error {
 	name := opts.ImageName
 	bus.Manager.Publish(bus.EventImagePrePull, opts)