Subject: Re: [PATCH 13/49] repack: move 'delta_base_offset' to 'struct pack_objects_args'

From: Taylor Blau <[email-masked]>
Date: Fri, 10 Oct 2025 18:54:50 -0400

On Fri, Oct 10, 2025 at 01:54:31AM -0400, Jeff King wrote:
> On Sun, Sep 28, 2025 at 06:08:00PM -0400, Taylor Blau wrote:
>
> > The static variable 'delta_base_offset' determines whether or not we
> > pass the "--delta-base-offset" command-line argument when spawning
> > pack-objects as a child process. Its introduction dates back to when
> > repack was rewritten in C, all the way back in a1bbc6c017 (repack:
> > rewrite the shell script in C, 2013-09-15).
> >
> > 'struct pack_objects_args' was introduced much later on in 4571324b99
> > (builtin/repack.c: allow configuring cruft pack generation, 2022-05-20),
> > but did not move the 'delta_base_offset' variable.
> >
> > Since the 'delta_base_offset' is a property of an individual
> > pack-objects command, re-introduce that variable as a member of 'struct
> > pack_objects_args', which will enable further code movement in the
> > subsequent commits.
>
> Hmm, OK. It is true that it is a property of a pack-objects invocation,
> but would we ever want it to be different between the two? I'd think
> not, and from what I can see:
>
> > +		cruft_po_args.delta_base_offset = po_args.delta_base_offset;
>
> we'd always use the same value in both cases. It kind of makes me wonder
> if it should be in the repack_ctx variable instead, then, with both
> pack-objects invocations pulling from a common source. But I could also
> believe that makes life harder later on, when you want to pass just the
> pack_objects_args to prepare_pack_objects().

Yeah, we do want to use the same value here in both cases. My thinking
when writing this patch was that whether or not we pass the
--delta-base-offset command-line argument to pack-objects *is* a
property of the pack-objects invocation.

But the fact that we want to use the same value when generating
reachable/geometric packs and when generating cruft packs is more of an
implementation detail of repack itself. I like that that detail is made
explicit in the line above.

Thanks,
Taylor