- fsync|sync! xapianonly|xapian-only
- indexlevel|L=s maxsize|max-size=s batchsize|batch-size=s
- sequentialshard|seq-shard|sequential-shard
+ fsync|sync! xapian_only|xapian-only
+ indexlevel|index-level|L=s max_size|max-size=s
+ batch_size|batch-size=s
+ sequential_shard|seq-shard|sequential-shard