cmd: add new describe-image command

This commit adds a new `describe-image` comamnd that contains
the details about the given image type. The output is yaml as
it is both nicely human readable and also machine readable.

The output looks like this:
```yaml
$ ./image-builder describe-image rhel-9.1 tar
distro: rhel-9.1
type: tar
arch: x86_64
os_vesion: "9.1"
bootmode: none
partition_type: ""
default_filename: root.tar.xz
packages:
  include:
    - policycoreutils
    - selinux-policy-targeted
    - selinux-policy-targeted
  exclude:
    - rng-tools
```

Thanks to Ondrej Budai for the idea and the example.

cmd/image-builder/describeimg.go

@@ -0,0 +1,89 @@
+package main
+
+import (
+	"io"
+	"slices"
+
+	"gopkg.in/yaml.v3"
+
+	"github.com/osbuild/images/pkg/blueprint"
+	"github.com/osbuild/images/pkg/distro"
+	"github.com/osbuild/images/pkg/imagefilter"
+)
+
+// Use yaml output by default because it is both nicely human and
+// machine readable and parts of our image defintions will be written
+// in yaml too.  This means this should be a possible input a
+// "flattended" image definiton.
+type describeImgYAML struct {
+	Distro string `yaml:"distro"`
+	Type   string `yaml:"type"`
+	Arch   string `yaml:"arch"`
+
+	// XXX: think about ordering (as this is what the user will see)
+	OsVersion string `yaml:"os_vesion"`
+
+	Bootmode        string `yaml:"bootmode"`
+	PartitionType   string `yaml:"partition_type"`
+	DefaultFilename string `yaml:"default_filename"`
+
+	// XXX: add pipelines here? maybe at least exports?
+	Packages *packagesYAML `yaml:"packages"`
+}
+
+type packagesYAML struct {
+	Include []string `yaml:"include"`
+	Exclude []string `yaml:"exclude"`
+}
+
+func packageSetsFor(imgType distro.ImageType) (inc, exc []string, err error) {
+	var bp blueprint.Blueprint
+	manifest, _, err := imgType.Manifest(&bp, distro.ImageOptions{}, nil, 0)
+	if err != nil {
+		return nil, nil, err
+	}
+
+	// XXX: or should this just do what osbuild-package-sets does
+	// and inlcude what pipeline needs the package set too?
+	for pipelineName, pkgSets := range manifest.GetPackageSetChains() {
+		// XXX: or shouldn't we exclude the build pipeline here?
+		if pipelineName == "build" {
+			continue
+		}
+		for _, pkgSet := range pkgSets {
+			inc = append(inc, pkgSet.Include...)
+			exc = append(exc, pkgSet.Exclude...)
+		}
+	}
+	slices.Sort(inc)
+	slices.Sort(exc)
+	return inc, exc, nil
+}
+
+// XXX: should this live in images instead?
+func describeImage(img *imagefilter.Result, out io.Writer) error {
+	// see
+	// https://github.com/osbuild/images/pull/1019#discussion_r1832376568
+	// for what is available on an image (without depsolve or partitioning)
+	inc, exc, err := packageSetsFor(img.ImgType)
+	if err != nil {
+		return err
+	}
+
+	outYaml := &describeImgYAML{
+		Distro:          img.Distro.Name(),
+		OsVersion:       img.Distro.OsVersion(),
+		Arch:            img.Arch.Name(),
+		Type:            img.ImgType.Name(),
+		Bootmode:        img.ImgType.BootMode().String(),
+		PartitionType:   img.ImgType.PartitionType().String(),
+		DefaultFilename: img.ImgType.Filename(),
+		Packages: &packagesYAML{
+			Include: inc,
+			Exclude: exc,
+		},
+	}
+	enc := yaml.NewEncoder(out)
+	enc.SetIndent(2)
+	return enc.Encode(outYaml)
+}

cmd/image-builder/describeimg_test.go

@@ -0,0 +1,41 @@
+package main_test
+
+import (
+	"bytes"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+
+	testrepos "github.com/osbuild/images/test/data/repositories"
+
+	"github.com/osbuild/image-builder-cli/cmd/image-builder"
+)
+
+func TestDescribeImage(t *testing.T) {
+	restore := main.MockNewRepoRegistry(testrepos.New)
+	defer restore()
+
+	res, err := main.GetOneImage("", "centos-9", "tar", "x86_64")
+	assert.NoError(t, err)
+
+	var buf bytes.Buffer
+	err = main.DescribeImage(res, &buf)
+	assert.NoError(t, err)
+
+	expectedOutput := `distro: centos-9
+type: tar
+arch: x86_64
+os_vesion: 9-stream
+bootmode: none
+partition_type: ""
+default_filename: root.tar.xz
+packages:
+  include:
+    - policycoreutils
+    - selinux-policy-targeted
+    - selinux-policy-targeted
+  exclude:
+    - rng-tools
+`
+	assert.Equal(t, expectedOutput, buf.String())
+}

cmd/image-builder/export_test.go

@@ -9,9 +9,10 @@ import (
 )
 
 var (
-	GetOneImage = getOneImage
-	Run         = run
-	FindDistro  = findDistro
+	GetOneImage   = getOneImage
+	Run           = run
+	FindDistro    = findDistro
+	DescribeImage = describeImage
 )
 
 func MockOsArgs(new []string) (restore func()) {

cmd/image-builder/main.go

@@ -108,6 +108,29 @@ func cmdBuild(cmd *cobra.Command, args []string) error {
 	return buildImage(res, mf.Bytes(), storeDir)
 }
 
+func cmdDescribeImg(cmd *cobra.Command, args []string) error {
+	// XXX: boilderplate identical to cmdManifest() above
+	dataDir, err := cmd.Flags().GetString("datadir")
+	if err != nil {
+		return err
+	}
+	archStr, err := cmd.Flags().GetString("arch")
+	if err != nil {
+		return err
+	}
+	if archStr == "" {
+		archStr = arch.Current().String()
+	}
+	distroStr := args[0]
+	imgTypeStr := args[1]
+	res, err := getOneImage(dataDir, distroStr, imgTypeStr, archStr)
+	if err != nil {
+		return err
+	}
+
+	return describeImage(res, osStdout)
+}
+
 func run() error {
 	// images logs a bunch of stuff to Debug/Info that is distracting
 	// the user (at least by default, like what repos being loaded)
@@ -161,6 +184,18 @@ operating sytsems like centos and RHEL with easy customizations support.`,
 	buildCmd.Flags().String("store", ".store", `osbuild store directory to cache intermediata build artifacts"`)
 	rootCmd.AddCommand(buildCmd)
 
+	// XXX: add --format=json too?
+	describeImgCmd := &cobra.Command{
+		Use:          "describe-image <distro> <image-type>",
+		Short:        "describe the given distro/image-type, e.g. centos-9 qcow2",
+		RunE:         cmdDescribeImg,
+		SilenceUsage: true,
+		Args:         cobra.ExactArgs(2),
+		Hidden:       true,
+	}
+	describeImgCmd.Flags().String("arch", "", `use the different architecture`)
+	rootCmd.AddCommand(describeImgCmd)
+
 	return rootCmd.Execute()
 }
 

cmd/image-builder/main_test.go

@@ -317,3 +317,25 @@ exit 1
 	// osbuild-exec.go)
 	assert.Equal(t, "error on stderr\n", fakeStderr.String())
 }
+
+func TestDescribeImageSmoke(t *testing.T) {
+	restore := main.MockNewRepoRegistry(testrepos.New)
+	defer restore()
+
+	restore = main.MockOsArgs([]string{
+		"describe-image",
+		"centos-9", "qcow2",
+	})
+	defer restore()
+
+	var fakeStdout bytes.Buffer
+	restore = main.MockOsStdout(&fakeStdout)
+	defer restore()
+
+	err := main.Run()
+	assert.NoError(t, err)
+
+	assert.Contains(t, fakeStdout.String(), `distro: centos-9
+type: qcow2
+arch: x86_64`)
+}