[PATCH] expand and clarify help for update

[Greg Ward]

On 28 October 2008, Adrian Buehlmann said:
> The patched part would end as:

This is following up the rewrite suggested by Hubert Kauker and refined
by me, right?  It seems like this particular help text is getting longer
and longer!

>     Use option -C to discard all uncommitted changes (no backups!) and
>     to discard any uncomitted 'hg merge', thus forcibly replacing the

"thus" is unnecessary here -- I suggest removing it.

Apart from that, it reads fine to me.

        Greg