qrsync 如何只根据hash判断更新

Question

根据此文章 http://segmentfault.com/q/1010000002391893
添加参数 --size-only

qrsync --check-exist --size-only conf.json
提示

Usage of qrsync:
  -check-exist=false: whether needs to check exist on dest

qrsync --size-only conf.json
提示:

flag provided but not defined: -size-only
Usage of qrsync:
  -check-exist=false: whether needs to check exist on dest

so? 倒底怎样使用??