traceTo :: History -> History -> Either String [TraceRecord]
traceTo start end = 
    impureCmd (\worker -> traceToWorker worker start end) start
traceTo :: History -> History -> Either String [TraceRecord]
traceTo start end = 
    impureCmd (\worker -> traceToWorker worker start end) start
traceTo start end = 
    impureCmd (\worker -> traceToWorker worker start end) start