Re: Fix branch ancestry calculation

[Keith Packard <keithp@keithp.com>]

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On Fri, 2006-03-24 at 20:45 -0500, Chris Shoemaker wrote:

> If that last sentence was a typo then you already know this, but
> otherwise you may be disappointed to learn that it's not _always_
> possible to discern the correct ancestry tree.

Sure, it's possible to generate trees which can't be figured out. So
far, I haven't found any which can't be pieced back together, except in
cases where the tree was accidentally damaged (child branches created on
two separate parent branches)

> If you end up comparing the ancestry tree discovered by your tool and
> the tree output by a patched cvsps, I would be very interested in the
> results.

So far, I've found several concrete trees where cvsps (in any form)
assigns branch points many versions too early compared to the 'true'
history. My tool is getting better answers, but still can't compute the
tree for the X.org X server tree yet. That one has a wide variety of
damage, including the direct copying of ,v files between repositories
which had divered, and the accidental branching of files from different
parent branches. I keep poking at it...

> -chris
> 
> (*) You can distinguish between A->B->head and B->A->head simply by
> date.

I'm doing a lot more date-based identification than I'm really
comfortable with; the bad thing here is that branch points can occur
long before any commits to that branch, when doing date-based
operations, you have a range of possible matching branch points and it's
hard to disambiguate.

-- 
keith.packard@intel.com

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