Re: Strange behavior of git rev-list

On Thu, Sep 7, 2017 at 3:11 AM, Jeff King [off-list ref] wrote:

On Thu, Sep 07, 2017 at 11:50:25AM +0200, Paweł Marczewski wrote:

quoted

Thanks. Any plans to fix that? Or is there a way to turn off this heuristic?

I don't think there's a way to turn it off for `rev-list`. Merge-base
computations are more careful, so you could determine the correct
endpoints that way. But when you fed them to `rev-list`, it would hit
the same run of skewed commits.

We've discussed storing true generation numbers in the past, which would
make this optimization more robust, as well as allow us to speed up many
other traversals (e.g., the "tag --contains"). It's something I'd like
to revisit, but it's not at the top of the pile.

(We just had an office discussion if this is part of the hash transition plan,
i.e. have a field in the commit object to contain its generation number.
and as I think the generation numbers would lead to fast and correct
behavior unlike the current heuristic which is only fast, I would try
to make a strong point actual generation numbers inside commit objects)

In the meantime, it would probably be possible to write a patch that
conditionally disables the optimization. But it would mean all of your
rev-lists run a _lot_ slower.

-Peff