Delay progress output until the transfer starts

If progress is not delayed it can interfere with credential helpers
asking for credentials to make the API calls.

lfs/progress_meter.go

@@ -22,6 +22,7 @@ type ProgressMeter struct {
 	estimatedBytes    int64
 	currentBytes      int64
 	skippedBytes      int64
+	started           int32
 	estimatedFiles    int
 	startTime         time.Time
 	finished          chan interface{}
@@ -38,7 +39,7 @@ func NewProgressMeter(estFiles int, estBytes int64, dryRun bool) *ProgressMeter
 		fmt.Fprintf(os.Stderr, "Error creating progress logger: %s\n", err)
 	}
 
-	pm := &ProgressMeter{
+	return &ProgressMeter{
 		logger:         logger,
 		startTime:      time.Now(),
 		fileIndex:      make(map[string]int64),
@@ -47,10 +48,12 @@ func NewProgressMeter(estFiles int, estBytes int64, dryRun bool) *ProgressMeter
 		estimatedBytes: estBytes,
 		dryRun:         dryRun,
 	}
+}
 
-	go pm.writer()
-
-	return pm
+func (p *ProgressMeter) Start() {
+	if atomic.SwapInt32(&p.started, 1) == 0 {
+		go p.writer()
+	}
 }
 
 // Add tells the progress meter that a transferring file is being added to the

lfs/transfer_queue.go

@@ -106,6 +106,7 @@ func (q *TransferQueue) individualApiRoutine(apiWaiter chan interface{}) {
 		}
 
 		if apiWaiter != nil { // Signal to launch more individual api workers
+			q.meter.Start()
 			select {
 			case apiWaiter <- 1:
 			default:
@@ -148,6 +149,8 @@ func (q *TransferQueue) legacyFallback(failedBatch []Transferable) {
 // making only one POST call for all objects. The results are then handed
 // off to the transfer workers.
 func (q *TransferQueue) batchApiRoutine() {
+	var startProgress sync.Once
+
 	for {
 		batch := q.batcher.Next()
 		if batch == nil {
@@ -174,6 +177,8 @@ func (q *TransferQueue) batchApiRoutine() {
 			continue
 		}
 
+		startProgress.Do(q.meter.Start)
+
 		for _, o := range objects {
 			if _, ok := o.Links[q.transferKind]; ok {
 				// This object needs to be transferred