Re: merge conflicts?

[<don...@is...>]

 > As a last resort, you can of course archive your current clisp checkout
 > and create a new one from scratch (hg clone ...).

This is not what I would have guessed.
Since I don't think I'm trying to write at all, I imagined that
this meant there was a conflict in what others were trying to write
and they would have to resolve the conflict before anyone could
proceed.

One of the posts,
https://stackoverflow.com/questions/12690557/mercurial-hg-abort-outstanding-uncommitted-merges
suggested:
 hg update --clean -r tip
and this does seem to solve the problem.
But I have no idea why.  Or why I should have to do that.
Should that be part of my nightly script?
Why shouldn't my previous
 hg pull -u
be enough?