I suspect that a "-" in place of a commit object name may not be
enough for your purpose, as the _number_ of parents can later
change in the later re-output.

I wonder if the presense of "incomplete" on the "Final output"
line is a good enough indication for that.  That is, until you
see "Final output: $N done", you will treat the parent
information as unreliable.
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I don't mind if a commit that has "-" as one of its parents later
turns out to have more parents (i.e. the "-" can stand for zero or
more unknown parents).  I would be perturbed if a commit that didn't
have any "-" in its parent list later turned out to have a different
number of parents - but I don't think that's what you're implying, is

The easiest way for me to handle an unreliable parent is just to
ignore it.  But I can't ignore all the parents, because then I
wouldn't have a graph at all.

In other words, the presence of "incomplete" doesn't give me any clue
as to which particular parent ids are reliable.  As far as I can see,
git log internally knows when a parent id is unreliable (it's one
where it had to terminate the history simplification early), so it
shouldn't be hard to tell gitk about that.  And it would make my job a
lot easier.

Paul.
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