feat(build): add flag to omit creation timestamp for reproducible builds

cmd/build.go

@@ -62,6 +62,7 @@ func init() {
 	// TODO: set the raw flag to true by default in future.
 	flags.BoolVar(&buildConfig.Raw, "raw", false, "turning on this flag will build model artifact layers in raw format")
 	flags.BoolVar(&buildConfig.Reasoning, "reasoning", false, "turning on this flag will mark this model as reasoning model in the config")
+	flags.BoolVar(&buildConfig.NoCreationTime, "no-creation-time", false, "turning on this flag will not set createdAt in the config, which will be helpful for repeated builds")
 
 	if err := viper.BindPFlags(flags); err != nil {
 		panic(fmt.Errorf("bind cache list flags to viper: %w", err))

pkg/backend/build.go

@@ -113,6 +113,7 @@ func (b *backend) Build(ctx context.Context, modelfilePath, workDir, target stri
 		SourceURL:      sourceInfo.URL,
 		SourceRevision: revision,
 		Reasoning:      cfg.Reasoning,
+		NoCreationTime: cfg.NoCreationTime,
 	}, layers)
 	if err != nil {
 		return fmt.Errorf("failed to build model config: %w", err)

pkg/backend/build/builder.go

@@ -257,15 +257,18 @@ func BuildModelConfig(modelConfig *buildconfig.Model, layers []ocispec.Descripto
 		}
 	}
 
-	createdAt := time.Now()
 	descriptor := modelspec.ModelDescriptor{
-		CreatedAt: &createdAt,
 		Family:    modelConfig.Family,
 		Name:      modelConfig.Name,
 		SourceURL: modelConfig.SourceURL,
 		Revision:  modelConfig.SourceRevision,
 	}
 
+	if !modelConfig.NoCreationTime {
+		createdAt := time.Now()
+		descriptor.CreatedAt = &createdAt
+	}
+
 	diffIDs := make([]godigest.Digest, 0, len(layers))
 	for _, layer := range layers {
 		diffIDs = append(diffIDs, layer.Digest)

pkg/backend/build/config/model.go

@@ -28,4 +28,5 @@ type Model struct {
 	SourceURL      string
 	SourceRevision string
 	Reasoning      bool
+	NoCreationTime bool
 }

pkg/config/build.go

@@ -35,6 +35,7 @@ type Build struct {
 	SourceRevision string
 	Raw            bool
 	Reasoning      bool
+	NoCreationTime bool
 }
 
 func NewBuild() *Build {
@@ -50,6 +51,7 @@ func NewBuild() *Build {
 		SourceRevision: "",
 		Raw:            false,
 		Reasoning:      false,
+		NoCreationTime: false,
 	}
 }