non-verbose ways to make sure Tarsnap is running

[David Prager Branner <brannerchinese@gmail.com>]

When a large backup is taking place, Tarsnap shows no signs of life. I've been using the -v option as a way of making sure it's alive and active. But I wonder if there isn't some less time-consuming way of letting it tell me that it's work — a slow-updating activity bar or something of that sort.

Thanks.

- dpb