// SaveBlob saves a blob of type t into the repository. If id is the null id, it
// will be computed and returned.
func (r *Repository) SaveBlob(t restic.BlobType, buf []byte, id restic.ID) (restic.ID, error) {
var i *restic.ID
if !id.IsNull() {
i = &id
}
return r.SaveAndEncrypt(t, buf, i)
}