func (t *BTTracer) PutDir(path string) error {
	t.Logf(LogDebug, "Uploading snapshots from %s...\n", path)
	return filepath.Walk(path, putDirWalk(t))
}
func (t *BTTracer) PutDir(path string) error {
	t.Logf(LogDebug, "Uploading snapshots from %s...\n", path)
	return filepath.Walk(path, putDirWalk(t))
}
// Synchronously uploads snapshots contained in the specified directory.
// It is safe to spawn a goroutine to run BTTracer.PutDir().
//
// ConfigurePut should have returned successfully before calling
// BTTracer.PutDir().
//
// Only files with the '.btt' suffix will be uploaded.
//
// The first error encountered terminates the directory walk, thus
// skipping snapshots which would have been processed later in the walk.