Re: [PATCH v5 0/5] log: speed up --follow following renames for non-linear history

[Miklos Vajna <vmiklos@collabora.com>]

Hi Patrick,

On Wed, Nov 11, 2026 at 11:43:50AM +0100, Patrick Steinhardt <ps@pks.im> wrote:
> > While the original patch and this series do improve correctness of
> > following a file through history, I wonder if the increased cost is
> > ultimately worth it in most scenarios. Maybe this could be something
> > opt-in with another flag instead of toggled on my default?
> 
> Yeah, by now I'm also leaning into this direction. The performance cost
> is definitely way too high for us, so we need a way to disable this new
> feature altogether at GitLab.

I have no problem with turning this from default to opt-in. I would be
happy to not revert, since a lot of effort went into this, and some see
this as a bug in git-log, not showing some history which is there.

> I don't have a strong sense on whether or not we should revert the whole
> series. I find the patches quite hard to review, but that may not be
> because we're fixing things incrementally and rather be because I myself
> am not familiar with this subsystem.
> 
> But in case we decide to not revert I'd like to see a toggle to disable
> this feature as a first step. As mentioned, this change has caused a
> rather big regression for GitLab, so we'd ideally have a way to disable
> this feature soon so that we can mitigate it.

Makes sense. To be honest, I'm not too happy about the complexity the
last patch in the series introduces -- but having performance that is
somewhat close to the old behavior seems to justify it.

> I don't want to make you (Miklos) responsible for delivering that of
> course, I just want us to align on a fast path forward. In case we don't
> revert we can help out and contribute such a default-disabled toggle.
> And if so, that would also give us more time to fix the issue properly.

Yes, aligning on what we want would be good. :-) I'm OK to replace the
last patch in the series with a patch that turns this off by default,
but then how to opt in, would be be fine to have a new config option for
this (similar to log.follow)? Would that do what you need or you want
something else?

Thanks,

Miklos