// We scanned a folder, optionally send update.
				f.updateCache.deleteRecursive(h)
				f.updateCache.copyWithChildren(&f.newCache, h, folder.parent)
				f.sendUpdate()
			}
		}

		// Transfer existing
		if !into.Compacted {
			for _, folder := range existingFolders {
				h := hashPath(folder.name)
				f.updateCache.copyWithChildren(&f.oldCache, h, folder.parent)
			}
		}
		// Scan new...

			if err := w.mw.Flush(); err != nil {
				return err
			}
			return s2w.Close()
		}
		return nil
	}
}

var s2DecPool = sync.Pool{New: func() interface{} {
	// Default alloc block for network transfer.
	return s2.NewReader(nil, s2.ReaderAllocBlock(16<<10))
}}

// metacacheReader allows reading a cache stream.
type metacacheReader struct {
	mr      *msgp.Reader
	current metaCacheEntry