fixes #8

> Currently, the value for "max empty response" is set to 10 and cannot
be modified via an option of the commandline command. However, we
discovered cases, were we run into this issue and I guess it would be
nice, if we could increase it a bit, to see whether we'll get some more
data out of the OAI endpoint.

cmd/metha-sync/main.go

@@ -24,6 +24,7 @@ func main() {
 	from := flag.String("from", "", "set the start date, format: 2006-01-02, use only if you do not want the endpoints earliest date")
 	quiet := flag.Bool("q", false, "suppress all output")
 	endpointList := flag.Bool("list", false, "list a selection of OAI endpoints (might be outdated)")
+	maxEmptyReponses := flag.Int("max-empty-responses", 10, "allow a number of empty responses before failing")
 
 	logFile := flag.String("log", "", "filename to log to")
 
@@ -80,7 +81,7 @@ func main() {
 	harvest.MaxRequests = *maxRequests
 	harvest.CleanBeforeDecode = true
 	harvest.DisableSelectiveHarvesting = *disableSelectiveHarvesting
-	harvest.MaxEmptyResponses = 10
+	harvest.MaxEmptyResponses = *maxEmptyReponses
 	harvest.IgnoreHTTPErrors = *ignoreHTTPErrors
 	harvest.SuppressFormatParameter = *suppressFormatParameter
 	harvest.DailyInterval = *daily