code: func (sis *SegmentInfos) replace(other *SegmentInfos) {
  	sis.rollbackSegmentInfos(other.Segments)
  	sis.lastGeneration = other.lastGeneration
  }
docs: // L1041
  /*
  Replaces all segments in this instance in this instance, but keeps
  generation, version, counter so that future commits remain write once.
  */