cmd: add new image-builder binary and initial list-images cmd

This commit adds a new `image-builder` binary that will (eventually)
be capable to build images standalone (daemonless). There are various
use-cases for this, the most important one is CI/CD pipelines but also
providing a common abstraction over the "images" library (and potentially
later "otk").

This commit implements basic a `list-images` command with filtering
and text and json output, e.g.
```
$ image-builder list-images --filter bootmode:none --filter name:fedora-39 --filter arch:s390x
fedora-39 --arch s390x --type container

$ ./image-builder list-images --filter bootmode:none --filter name:fedora-39 --filter arch:s390x --format=json
{"distro":{"name":"fedora-39"},"arch":{"name":"s390x"},"image_type":{"name":"container"}}
```

cmd/image-builder/export_test.go

@@ -0,0 +1,26 @@
+package main
+
+import (
+	"io"
+	"os"
+)
+
+func MockOsArgs(new []string) (restore func()) {
+	saved := os.Args
+	os.Args = append([]string{"argv0"}, new...)
+	return func() {
+		os.Args = saved
+	}
+}
+
+func MockOsStdout(new io.Writer) (restore func()) {
+	saved := osStdout
+	osStdout = new
+	return func() {
+		osStdout = saved
+	}
+}
+
+var (
+	Run = run
+)

cmd/image-builder/list_images.go

@@ -0,0 +1,48 @@
+package main
+
+import (
+	"io"
+	"os"
+	"strings"
+
+	"github.com/osbuild/images/pkg/distrofactory"
+	"github.com/osbuild/images/pkg/reporegistry"
+)
+
+// XXX: copied from "composer", should be exported there so
+// that we keep this in sync
+// XXX2: means we need to depend on osbuild-composer-common or something
+var repositoryConfigs = []string{
+	"/etc/osbuild-composer",
+	"/usr/share/osbuild-composer",
+}
+
+func listImages(out io.Writer, format string, filterExprs []string) error {
+	// useful for development/debugging, e.g. run:
+	// go build && IMAGE_BUILDER_EXTRA_REPOS_PATH=../../test/data ./image-builder
+	if extraReposPath := os.Getenv("IMAGE_BUILDER_EXTRA_REPOS_PATH"); extraReposPath != "" {
+		repositoryConfigs = append(repositoryConfigs, strings.Split(extraReposPath, ":")...)
+	}
+
+	repos, err := reporegistry.New(repositoryConfigs)
+	if err != nil {
+		return err
+	}
+	filters, err := NewFilters(filterExprs)
+	if err != nil {
+		return err
+	}
+	fac := distrofactory.NewDefault()
+	filteredResult, err := FilterDistros(fac, repos.ListDistros(), filters)
+	if err != nil {
+		return err
+	}
+
+	fmter, err := NewFilteredResultFormatter(format)
+	if err != nil {
+		return err
+	}
+	fmter.Output(out, filteredResult)
+
+	return nil
+}

cmd/image-builder/main.go

@@ -0,0 +1,61 @@
+package main
+
+import (
+	"io"
+	"log"
+	"os"
+
+	"github.com/sirupsen/logrus"
+
+	"github.com/spf13/cobra"
+)
+
+var osStdout io.Writer = os.Stdout
+
+func cmdListImages(cmd *cobra.Command, args []string) error {
+	filter, err := cmd.Flags().GetStringArray("filter")
+	if err != nil {
+		return err
+	}
+	format, err := cmd.Flags().GetString("format")
+	if err != nil {
+		return err
+	}
+
+	return listImages(osStdout, format, filter)
+}
+
+func run() error {
+	// images logs a bunch of stuff to Debug/Info that we we do not
+	// want to show
+	logrus.SetLevel(logrus.WarnLevel)
+
+	rootCmd := &cobra.Command{
+		Use:   "image-builder",
+		Short: "Build operating system images from a given blueprint",
+		Long: `Build operating system images from a given blueprint
+
+Image-builder builds operating system images for a range of predefined
+operating sytsems like centos and RHEL with easy customizations support.`,
+	}
+
+	// XXX: this will list 802 images right now, we need a sensible
+	// default here, maybe without --filter just list all available
+	// distro names?
+	listImagesCmd := &cobra.Command{
+		Use:          "list-images",
+		RunE:         cmdListImages,
+		SilenceUsage: true,
+	}
+	listImagesCmd.Flags().StringArray("filter", nil, "Filter distributions by a specific criteria")
+	listImagesCmd.Flags().String("format", "", "Output in a specific format (text,json)")
+	rootCmd.AddCommand(listImagesCmd)
+
+	return rootCmd.Execute()
+}
+
+func main() {
+	if err := run(); err != nil {
+		log.Fatalf("error: %s", err)
+	}
+}

cmd/image-builder/main_test.go

@@ -0,0 +1,26 @@
+package main_test
+
+import (
+	"bytes"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+
+	"github.com/osbuild/images/cmd/image-builder"
+)
+
+func TestListImagesSmoke(t *testing.T) {
+	t.Setenv("IMAGE_BUILDER_EXTRA_REPOS_PATH", "../../test/data")
+
+	restore := main.MockOsArgs([]string{"list-images"})
+	defer restore()
+
+	var fakeStdout bytes.Buffer
+	restore = main.MockOsStdout(&fakeStdout)
+	defer restore()
+
+	err := main.Run()
+	assert.NoError(t, err)
+	// output is sorted
+	assert.Regexp(t, `(?ms)rhel-8.9.*rhel-8.10`, fakeStdout.String())
+}