manifest: add SerializeOptions to manifest.Serialize()

This commit makes `Serialize()` more extensible by switching the
rpmDownloader option to a more general `SerializeOptions` struct
that can be nil if no options are required. It contains the
`RpmDownloader` as the only option right now. We could YAGNI it
and do it once we have the second option but arguably it is cleaner
already doing it now.

cmd/build/main.go

@@ -81,7 +81,7 @@ func makeManifest(
 		return nil, fmt.Errorf("[ERROR] ostree commit resolution failed: %w", err)
 	}
 
-	mf, err := manifest.Serialize(depsolvedSets, containerSpecs, commitSpecs, 0)
+	mf, err := manifest.Serialize(depsolvedSets, containerSpecs, commitSpecs, nil)
 	if err != nil {
 		return nil, fmt.Errorf("[ERROR] manifest serialization failed: %w", err)
 	}

cmd/gen-manifests/main.go

@@ -249,7 +249,7 @@ func makeManifestJob(
 			commitSpecs = mockResolveCommits(manifest.GetOSTreeSourceSpecs())
 		}
 
-		mf, err := manifest.Serialize(depsolvedSets, containerSpecs, commitSpecs, 0)
+		mf, err := manifest.Serialize(depsolvedSets, containerSpecs, commitSpecs, nil)
 		if err != nil {
 			return fmt.Errorf("[%s] manifest serialization failed: %s", filename, err.Error())
 		}

cmd/osbuild-playground/playground.go

@@ -49,7 +49,7 @@ func RunPlayground(img image.ImageKind, d distro.Distro, arch distro.Arch, repos
 		fmt.Fprintf(os.Stderr, "could not clean dnf cache: %s", err.Error())
 	}
 
-	bytes, err := manifest.Serialize(depsolvedSets, nil, nil, 0)
+	bytes, err := manifest.Serialize(depsolvedSets, nil, nil, nil)
 	if err != nil {
 		panic("failed to serialize manifest: " + err.Error())
 	}

pkg/manifest/manifest.go

@@ -141,7 +141,15 @@ func (m Manifest) GetOSTreeSourceSpecs() map[string][]ostree.SourceSpec {
 	return ostreeSpecs
 }
 
-func (m Manifest) Serialize(depsolvedSets map[string]dnfjson.Result, containerSpecs map[string][]container.Spec, ostreeCommits map[string][]ostree.CommitSpec, rpmDownloader osbuild.RpmDownloader) (OSBuildManifest, error) {
+type SerializeOptions struct {
+	RpmDownloader osbuild.RpmDownloader
+}
+
+func (m Manifest) Serialize(depsolvedSets map[string]dnfjson.Result, containerSpecs map[string][]container.Spec, ostreeCommits map[string][]ostree.CommitSpec, opts *SerializeOptions) (OSBuildManifest, error) {
+	if opts == nil {
+		opts = &SerializeOptions{}
+	}
+
 	for _, pipeline := range m.pipelines {
 		pipeline.serializeStart(Inputs{
 			Depsolved:  depsolvedSets[pipeline.Name()],
@@ -165,7 +173,7 @@ func (m Manifest) Serialize(depsolvedSets map[string]dnfjson.Result, containerSp
 		pipeline.serializeEnd()
 	}
 
-	sources, err := osbuild.GenSources(mergedInputs, rpmDownloader)
+	sources, err := osbuild.GenSources(mergedInputs, opts.RpmDownloader)
 	if err != nil {
 		return nil, err
 	}