On 2020-07-23 at 04:15:37, Junio C Hamano wrote:
> "brian m. carlson" <sandals@crustytoothpaste.net> writes:
> 
> >> By declaring that the repository is invalid if its version is less
> >> than 1 and objectFormat extension defined, we prevent unwanted
> >> upgrading from happening by mistake.
> >
> > Yes, and more specifically:
> >
> > * If the repository is v0 and has an objectFormat set, we fail in newer
> >   versions of Git (i.e., after this series).  Older versions which do
> >   not support the extension will see breakage (because unknown
> >   extensions are not fatal in v0), but we hope by adding this check that
> >   nobody will ever configure a repo this way, since it will be totally
> >   nonfunctional in this state, regardless of version.
> > * If the repository is v1 and has an objectFormat set, we work with
> >   newer Git and everything is great.  Older Git versions fail hard here,
> >   and the user gets a moderately helpful error message.
> >
> > v2 of the series just ignored the setting in v0, which would make it
> > equally broken in older and newer versions, but would provide a less
> > useful error message (probably about a corrupt index).
> 
> Peff's 'jk/reject-newer-extensions-in-v0' uses a bit refactored code
> to make it easier to add only-v1-and-later extensions while rejecting
> them, even if the code knows about them, in v0 repository.  Even
> though the mechanism is a bit different, the spirit is quite the
> same as this step.
> 
> Please double check origin/seen:setup.c to see if I resolved textual
> conflicts in a sensible way.

Yes, this seems quite sensible, and exactly the resolution I was hoping
for.
-- 
brian m. carlson: Houston, Texas, US