code: func (t *Tag) Blob() (*Blob, error) {
  	if t.TargetType != plumbing.BlobObject {
  		return nil, ErrUnsupportedObject
  	}
  
  	return GetBlob(t.s, t.Target)
  }
docs: // Blob returns the blob pointed to by the tag. If the tag points to a
  // different type of object ErrUnsupportedObject will be returned.