overfetch param

main.go

@@ -74,6 +74,7 @@ var cli struct {
 	Sync struct {
 		Existing string `arg:"" type:"existingfile"`
 		Syncfile string `arg:"" type:"existingfile"`
+		Overfetch       float32 `default:0.05 help:"What ratio of extra data to download to minimize # requests; 0.2 is 20%"`
 	} `cmd:"" hidden:""`
 
 	Serve struct {
@@ -202,7 +203,7 @@ func main() {
 			logger.Fatalf("Failed to makesync archive, %v", err)
 		}
 	case "sync <existing> <syncfile>":
-		err := pmtiles.Sync(logger, cli.Sync.Existing, cli.Sync.Syncfile)
+		err := pmtiles.Sync(logger, cli.Sync.Existing, cli.Sync.Syncfile, cli.Sync.Overfetch)
 		if err != nil {
 			logger.Fatalf("Failed to sync archive, %v", err)
 		}

pmtiles/makesync.go

@@ -255,7 +255,7 @@ func Makesync(logger *log.Logger, cli_version string, file string, block_size_kb
 	return nil
 }
 
-func Sync(logger *log.Logger, file string, syncfilename string) error {
+func Sync(logger *log.Logger, file string, syncfilename string, overfetch float32) error {
 	start := time.Now()
 
 	syncfile, err := os.Open(syncfilename)
@@ -421,7 +421,6 @@ func Sync(logger *log.Logger, file string, syncfilename string) error {
 		ranges = append(ranges,SrcDstRange{SrcOffset:v.Offset,DstOffset:v.Offset,Length:v.Length})
 	}
 
-	overfetch := float32(0.05)
 	requests, _ := MergeRanges(ranges, overfetch)
 	fmt.Printf("need %d requests with overfetch=%f.\n", requests.Len(), overfetch)