What's the best way to execute a Mercurial command from an extension?

[Paul Moore]

I want to write an extension which basically pulls together a series
of Mercurial commands, and I'm not sure what the best way to do this
is.

It looks to me like the "canonical" interface for most commands is

    mercurial.commands.command_name(ui, repo, *other_args, **kw_args)

Is that a sensible way of calling an arbitrary command?

Also, I need to call the mq "strip" command. It appears that I can do this via

    from hgext.mq import strip
    strip(ui, repo, rev)

But what will happen if the mq extension is not present? A quick
experiment indicates that it will work whether or not mq is enabled
(in mercurial.ini) - is it OK to use it regardless? Furthermore, is it
possible for the import given to fail (and if so, should I check for
an exception and report the error if so)? Or am I worrying too much,
and because mq is distributed with Mercurial, it's OK to use it
regardless of whether the user enables the extension?

Thanks,
Paul.