On Mon, Sep 12, 2016 at 11:23:18PM -0700, Junio C Hamano wrote:
> Kirill Smelkov <k...@nexedi.com> writes:
>
> > +static int want_found_object(int exclude, struct packed_git *p)
> > +{
> > + if (exclude)
> > + return 1;
> > + if (incremental)
> > + return 0;
> > +
> > + /*
> > + * When asked to do --local (do not include an object that appears in a
> > + * pack we borrow from elsewhere) or --honor-pack-keep (do not include
> > + * an object that appears in a pack marked with .keep), finding a pack
> > + * that matches the criteria is sufficient for us to decide to omit it.
> > + * However, even if this pack does not satisfy the criteria, we need to
> > + * make sure no copy of this object appears in _any_ pack that makes us
> > + * to omit the object, so we need to check all the packs.
> > + *
> > + * We can however first check whether these options can possible matter;
> > + * if they do not matter we know we want the object in generated pack.
> > + * Otherwise, we signal "-1" at the end to tell the caller that we do
> > + * not know either way, and it needs to check more packs.
> > + */
> > + if (!ignore_packed_keep &&
> > + (!local || !have_non_local_packs))
> > + return 1;
> > +
> > + if (local && !p->pack_local)
> > + return 0;
> > + if (ignore_packed_keep && p->pack_local && p->pack_keep)
> > + return 0;
> > +
> > + /* we don't know yet; keep looking for more packs */
> > + return -1;
> > +}
>
> Moving this logic out to this helper made the main logic in the
> caller easier to grasp.
>
> > @@ -958,15 +993,30 @@ static int want_object_in_pack(const unsigned char
> > *sha1,
> > off_t *found_offset)
> > {
> > struct packed_git *p;
> > + int want;
> >
> > if (!exclude && local && has_loose_object_nonlocal(sha1))
> > return 0;
> >
> > + /*
> > + * If we already know the pack object lives in, start checks from that
> > + * pack - in the usual case when neither --local was given nor .keep
> > files
> > + * are present we will determine the answer right now.
> > + */
> > + if (*found_pack) {
> > + want = want_found_object(exclude, *found_pack);
> > + if (want != -1)
> > + return want;
> > + }
> >
> > for (p = packed_git; p; p = p->next) {
> > + off_t offset;
> > +
> > + if (p == *found_pack)
> > + offset = *found_offset;
> > + else
> > + offset = find_pack_entry_one(sha1, p);
> > +
> > if (offset) {
> > if (!*found_pack) {
> > if (!is_pack_valid(p))
> > @@ -974,31 +1024,9 @@ static int want_object_in_pack(const unsigned char
> > *sha1,
> > *found_offset = offset;
> > *found_pack = p;
> > }
> > + want = want_found_object(exclude, p);
> > + if (want != -1)
> > + return want;
> > }
> > }
>
> As Peff noted in his earlier review, however, MRU code needed to be
> grafted in to the caller (an update to the MRU list was done in the
> code that was moved to the want_found_object() helper). I think I
> did it correctly, which ended up looking like this:
>
> want = want_found_object(exclude, p);
> if (!exclude && want > 0)
> mru_mark(packed_git_mru, entry);
> if (want != -1)
> return want;
>
> I somewhat feel that it is ugly that the helper knows about exclude
> (i.e. in the original code, we immediately returned 1 without
> futzing with the MRU when we find an entry that is to be excluded,
> which now is done in the helper), and the caller also knows about
> exclude (i.e. the caller knows that the helper may return positive
> in two cases, it knows that MRU marking needs to happen only one of
> the two cases, and it also knows that "exclude" is what
> differentiates between the two cases) at the same time.
>
> But probably the reason why I feel it ugly is only because I knew
> how the original looked like. I dunno.
Junio, the code above is correct semantic merge of pack-mru and my
topic, because in pack-mru if found and exclude=1, 1 was returned
without marking found pack.
But I wonder: even if we exclude an object, we were still looking for it
in packs, and when we found it, we found the corresponding pack too. So,
that pack _was_ most-recently-used, and it is correct to mark it as MRU.
We can do the simplification in the follow-up patch after the merge, so
merge does not change semantics and it is all bisectable, etc.
Jeff?
