Extracting bare revision numbers from $ hg log (or something similar)

[Alan Mackenzie]

Hello, Mercurial.

I can get an hg log of revisions I'm interested in with a command like
the following:

    $ hg log -b default -X.hgtags -rdefault:5389

.  What I really want is just the revision numbers, so that I can feed
these through into a script.  Of course, I could extract these revision
numbers myself from the result of the 'hg log ...', but it strikes me
there surely must be an hg command I can feed the parameters

    -b default -X.hgtags -rdefault:5389

into to get a list of wanted revisions.  I haven't been able to find any
such command by perusing the hg man page.  Is there one?

If there isn't such a command, is there some other way of doing what I
want which is less work (including reading documentation) than writing a
script to extract them from the output of the log command?

Thanks in advance!

-- 
Alan Mackenzie (Nuremberg, Germany).