fix: check tag existence during build (#85)

Signed-off-by: chlins <[email protected]>

Author: chlins

go.mod

@@ -3,7 +3,7 @@ module github.com/CloudNativeAI/modctl
 go 1.23.3
 
 require (
-	github.com/CloudNativeAI/model-spec v0.0.0-20250212030633-7aabe2b8eadc
+	github.com/CloudNativeAI/model-spec v0.0.1
 	github.com/distribution/distribution/v3 v3.0.0-rc.3
 	github.com/distribution/reference v0.6.0
 	github.com/dustin/go-humanize v1.0.1

go.sum

@@ -1,5 +1,5 @@
-github.com/CloudNativeAI/model-spec v0.0.0-20250212030633-7aabe2b8eadc h1:EmVmYn5o4jGweOlvjsbsdeSlSpNYvWPQ2muLaQXT1L8=
-github.com/CloudNativeAI/model-spec v0.0.0-20250212030633-7aabe2b8eadc/go.mod h1:3U/4zubBfbUkW59ATSg41HnkYyKrKUcKFH/cVdoPQnk=
+github.com/CloudNativeAI/model-spec v0.0.1 h1:BgVIStKTLuL1DrLC5A/gmHcR8TEhFCDz9+fYdCUa/CY=
+github.com/CloudNativeAI/model-spec v0.0.1/go.mod h1:3U/4zubBfbUkW59ATSg41HnkYyKrKUcKFH/cVdoPQnk=
 github.com/VividCortex/ewma v1.2.0 h1:f58SaIzcDXrSy3kWaHNvuJgJ3Nmz59Zji6XoJR/q1ow=
 github.com/VividCortex/ewma v1.2.0/go.mod h1:nz4BbCtbLyFDeC9SUHbtcT5644juEuWfUAUnGx7j5l4=
 github.com/acarl005/stripansi v0.0.0-20180116102854-5a71ef0e047d h1:licZJFw2RwpHMqeKTCYkitsPqHNxTmd4SNR5r94FGM8=

pkg/backend/build.go

@@ -43,6 +43,10 @@ func (b *backend) Build(ctx context.Context, modelfilePath, workDir, target stri
 	}
 
 	repo, tag := ref.Repository(), ref.Tag()
+	if tag == "" {
+		return fmt.Errorf("tag is required")
+	}
+
 	layers := []ocispec.Descriptor{}
 	layerDescs, err := b.process(ctx, workDir, repo, b.getProcessors(modelfile)...)
 	if err != nil {