Re: [PATCH 1/4] pack-bitmap: write lookup table extension by default

From: Taylor Blau <me@ttaylorr.com>
Date: Apr 18, 2025, 21:52 UTC
Message-ID: <aALJoFOUWq0v3fiB@nand.local>
In-Reply-To: <xmqqr01pbhk2.fsf@gitster.g>

On Fri, Apr 18, 2025 at 08:44:29AM -0700, Junio C Hamano wrote:

Show 15 quoted lines

> Jeff King <peff@peff.net> writes:
>
> > They're not technically required to be in sync. It is OK for the midx
> > bitmaps to have different options than the ones we make for packs. And
> > in theory they could intentionally diverge, though in practice I don't
> > think we (yet) have any extensions or options that would be more
> > appropriate for one or the other.
> >
> > So if we did want to join them, I think it would make sense to still be
> > able to use different flags for each situation, but initialize them from
> > a common definition.
>
> Thanks for great explanation---I guess it is not worth pursuing,
> then.  It is not like it would make the system misbehave when two
> are set differently.

Hah, Peff beat me to it. I saw your reply last night and was going to write you a very similar response.

I think the summary from my perspective would be that: the two could fall out-of-sync intentionally if we want the two commands to ever have different defaults. Tangentially we could use some common "bitmap_flags" field whose bits are defined in pack-bitmap.h and used in both places.

The latter is a bit awkward currently because the current "flags" that we pass into the MIDX machinery from the builtin all have MIDX-specific meanings. So we would have to either make sure that MIDX uses separate bit positions (which is awful and far too fragile for my comfort/taste) or store them as a separate set of flags (I think what Peff is getting at above).

Thanks, Taylor