Re: [PATCH 1/2] Revert "check_repository_format_gently(): refuse extensions for old repositories"

[Jeff King <peff@peff.net>]

On Wed, Jul 15, 2020 at 11:24:29PM -0700, Jonathan Nieder wrote:

> The behavior introduced in 14c7fa269e4 might be a good behavior if we
> were traveling back in time to 2015, but we're far too late.  For some
> reason I thought that it was what had been originally implemented and
> that it had regressed.  Apologies for not doing my research when
> 14c7fa269e4 was under development.

Thanks for a good summary of the situation. I agree that the current
(well, pre-14c7fa269e4) behavior is a bug (mine) from 2015, and we
probably have to accept that state of affairs to some degree in order to
avoid breaking existing cases.

It is unfortunate that this means that somebody with version=0 and
extensions.preciousObjects is in danger of running a pre-2015 version of
Git and having that extension totally ignored, which could be a
data-safety issue. But the farther we get from 2015 the less likely that
is to be a problem (and the more likely somebody is to be depending on
the current behavior of v0+preciousObjects).

> Let's return to the behavior we've had since 2015: always act on
> extensions.* settings, regardless of repository format version.  While
> we're here, include some tests to describe the effect on the "upgrade
> repository version" code path.

So this makes sense to me as a first step.

-Peff