Re: [PATCH 1/2] pack-objects: break out of want_object loop early

On Mon, Jul 25, 2016 at 02:52:24PM -0700, Junio C Hamano wrote:

Jeff King [off-list ref] writes:

quoted

  if (!*found_pack) {
    ... first find! fill in found pack, etc ...
  }
  if (exclude)
	return 1;
  if (incremental)
	return 0;
  if (!ignore_packed_keep && !local)
	break; /* effectively return 1, but I think the break is more clear */
  if (local && !p->pack_local)
	return 0;
  if (ignore_packed_keep && p->pack_local && p->pack_keep)
	return 0;

which just bumps it up. I don't think there is a way to make it more
elegant, e.g., by only checking ignore_packed_keep once, because we have
to distinguish between each condition being set independently, or the
case where neither is set.

So I stuck the new check at the end, because to me logically it was "can
we break out of the loop instead of looking at p->next". But I agree it
would be equivalent to place it before the related checks, and I don't
mind doing that if you think it's more readable.

I do not mind too much about having to check two bools twice.  But
given that the reason why I was confused was because I didn't see
why we need to pass the two "return 0" conditions at least once
before we decide that we do not need the "return 0" thing at all,
and started constructing a case where this might break by writing
"Suppose you have two packs, one remote and one local in packed_git
list in this order, and ..." before I realized that the new "early
break" can be hoisted up like the above, I definitely feel that "we
found one, and we aren't conditionally pretending that this thing
does not need to be packed at all, so return early and say we want
to pack it" is easier to understand before the two existing "if"
statements.

Ah, right. Now you had me second-guessing for a moment that there might
be a bad case in hoisting it up where we would want to return 0 but
would break out early to the "return 1".

But it cannot be the case, because the break is mutually exclusive with
the two conditions.

-Peff