Add CreateTar to image API

Add api call which uses go-container registry to create OCI images from
standard tar archives.

Consume new API when generating final images instead of docker building them
and adapts/add tests as necessary.

This change now allows to carry over xattrs to final images.

Fixes #266

pkg/api/core/image/create_test.go

@@ -0,0 +1,79 @@
+// Copyright © 2021 Ettore Di Giacinto <mudler@gentoo.org>
+//
+// This program is free software; you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation; either version 2 of the License, or
+// (at your option) any later version.
+//
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License along
+// with this program; if not, see <http://www.gnu.org/licenses/>.
+
+package image_test
+
+import (
+	"os"
+	"path/filepath"
+
+	. "github.com/mudler/luet/pkg/api/core/image"
+	"github.com/mudler/luet/pkg/api/core/types"
+	"github.com/mudler/luet/pkg/api/core/types/artifact"
+	"github.com/mudler/luet/pkg/compiler/backend"
+	"github.com/mudler/luet/pkg/helpers/file"
+	. "github.com/onsi/ginkgo"
+	. "github.com/onsi/gomega"
+)
+
+var _ = Describe("Create", func() {
+	Context("Creates an OCI image from a standard tar", func() {
+		It("creates an image which is loadable", func() {
+			ctx := types.NewContext()
+
+			dst, err := ctx.Config.System.TempFile("dst")
+			Expect(err).ToNot(HaveOccurred())
+			defer os.RemoveAll(dst.Name())
+			srcTar, err := ctx.Config.System.TempFile("srcTar")
+			Expect(err).ToNot(HaveOccurred())
+			defer os.RemoveAll(srcTar.Name())
+
+			b := backend.NewSimpleDockerBackend(ctx)
+
+			b.DownloadImage(backend.Options{ImageName: "alpine"})
+			img, err := b.ImageReference("alpine", false)
+			Expect(err).ToNot(HaveOccurred())
+
+			_, dir, err := Extract(ctx, img, false, nil)
+			Expect(err).ToNot(HaveOccurred())
+
+			defer os.RemoveAll(dir)
+
+			Expect(file.Touch(filepath.Join(dir, "test"))).ToNot(HaveOccurred())
+			Expect(file.Exists(filepath.Join(dir, "bin"))).To(BeTrue())
+
+			a := artifact.NewPackageArtifact(srcTar.Name())
+			a.Compress(dir, 1)
+
+			// Unfortunately there is no other easy way to test this
+			err = CreateTar(srcTar.Name(), dst.Name(), "testimage")
+			Expect(err).ToNot(HaveOccurred())
+
+			b.LoadImage(dst.Name())
+
+			Expect(b.ImageExists("testimage")).To(BeTrue())
+
+			img, err = b.ImageReference("testimage", false)
+			Expect(err).ToNot(HaveOccurred())
+
+			_, dir, err = Extract(ctx, img, false, nil)
+			Expect(err).ToNot(HaveOccurred())
+
+			defer os.RemoveAll(dir)
+			Expect(file.Exists(filepath.Join(dir, "bin"))).To(BeTrue())
+			Expect(file.Exists(filepath.Join(dir, "test"))).To(BeTrue())
+		})
+	})
+})