cmd/describe: fix describing of OSTree images

OSTree images require additional arguments to serialize their Manifest.
The 'describe' command was not setting those, which resulted in errors
when describing such image types.

Set the required minimum OSTree arguments to dummy values to enable
describing of such images.

Signed-off-by: Tomáš Hozza <thozza@redhat.com>

cmd/image-builder/describeimg.go

@@ -13,6 +13,7 @@ import (
 	"github.com/osbuild/images/pkg/distro"
 	"github.com/osbuild/images/pkg/distro/defs"
 	"github.com/osbuild/images/pkg/imagefilter"
+	"github.com/osbuild/images/pkg/ostree"
 )
 
 // Use yaml output by default because it is both nicely human and
@@ -45,7 +46,16 @@ type packagesYAML struct {
 
 func packageSetsFor(imgType distro.ImageType) (map[string]*packagesYAML, error) {
 	var bp blueprint.Blueprint
-	manifest, _, err := imgType.Manifest(&bp, distro.ImageOptions{}, nil, nil)
+
+	var imgOpts distro.ImageOptions
+	// Mock ostree options for ostree-based images to make describe work
+	if imgType.OSTreeRef() != "" {
+		imgOpts.OSTree = &ostree.ImageOptions{
+			URL: "http://example.com/repo",
+		}
+	}
+
+	manifest, _, err := imgType.Manifest(&bp, imgOpts, nil, nil)
 	if err != nil {
 		return nil, err
 	}