Re: [PATCH v2 2/3] merge-ort: shuffle the computation and cleanup of potential collisions

[Elijah Newren <newren@gmail.com>]

On Thu, Jun 30, 2022 at 3:29 AM Ævar Arnfjörð Bjarmason
<avarab@gmail.com> wrote:
>
> On Thu, Jun 30 2022, Elijah Newren via GitGitGadget wrote:
>
> > From: Elijah Newren <newren@gmail.com>
> >
> > Run compute_collisions() for renames on both sides of history before
> > any calls to collect_renames(), and do not free the computed collisions
> > until after both calls to collect_renames().  This is just a code
> > reorganization at this point that doesn't make sense on its own, but
> > will permit us to use the computed collision info from both sides
> > within each call to collect_renames() in a subsequent commit.
>
> I think this would be easier to follow if split in two, since...
>
> > +static void free_collisions(struct strmap *collisions)
> > +{
> > +     struct hashmap_iter iter;
> > +     struct strmap_entry *entry;
> > +
> > +     /* Free each value in the collisions map */
> > +     strmap_for_each_entry(collisions, &iter, entry) {
> > +             struct collision_info *info = entry->value;
> > +             string_list_clear(&info->source_files, 0);
> > +     }
> > +     /*
> > +      * In compute_collisions(), we set collisions.strdup_strings to 0
> > +      * so that we wouldn't have to make another copy of the new_path
> > +      * allocated by apply_dir_rename().  But now that we've used them
> > +      * and have no other references to these strings, it is time to
> > +      * deallocate them.
> > +      */
> > +     free_strmap_strings(collisions);
> > +     strmap_clear(collisions, 1);
> > +}
>
> ...a large part of it...
> >
> > -     /* Free each value in the collisions map */
> > -     strmap_for_each_entry(&collisions, &iter, entry) {
> > -             struct collision_info *info = entry->value;
> > -             string_list_clear(&info->source_files, 0);
> > -     }
> > -     /*
> > -      * In compute_collisions(), we set collisions.strdup_strings to 0
> > -      * so that we wouldn't have to make another copy of the new_path
> > -      * allocated by apply_dir_rename().  But now that we've used them
> > -      * and have no other references to these strings, it is time to
> > -      * deallocate them.
> > -      */
> > -     free_strmap_strings(&collisions);
> > -     strmap_clear(&collisions, 1);
>
> ..is moving existing code into a utility function...
>
> >       return clean;
> >  }
> >
> > @@ -3100,6 +3105,7 @@ static int detect_and_process_renames(struct merge_options *opt,
> >  {
> >       struct diff_queue_struct combined = { 0 };
> >       struct rename_info *renames = &opt->priv->renames;
> > +     struct strmap collisions[3];
> >       int need_dir_renames, s, i, clean = 1;
> >       unsigned detection_run = 0;
> >
> > @@ -3149,12 +3155,22 @@ static int detect_and_process_renames(struct merge_options *opt,
> >       ALLOC_GROW(combined.queue,
> >                  renames->pairs[1].nr + renames->pairs[2].nr,
> >                  combined.alloc);
> > +     for (int i = MERGE_SIDE1; i <= MERGE_SIDE2; i++) {
> > +             int other_side = 3 - i;
> > +             compute_collisions(&collisions[i],
> > +                                &renames->dir_renames[other_side],
> > +                                &renames->pairs[i]);
> > +     }
> >       clean &= collect_renames(opt, &combined, MERGE_SIDE1,
> > +                              collisions,
> >                                &renames->dir_renames[2],
> >                                &renames->dir_renames[1]);
> >       clean &= collect_renames(opt, &combined, MERGE_SIDE2,
> > +                              collisions,
> >                                &renames->dir_renames[1],
> >                                &renames->dir_renames[2]);
> > +     for (int i = MERGE_SIDE1; i <= MERGE_SIDE2; i++)
> > +             free_collisions(&collisions[i]);
> >       STABLE_QSORT(combined.queue, combined.nr, compare_pairs);
> >       trace2_region_leave("merge", "directory renames", opt->repo);
>
> ...which when looking at it makes the functional change harder to follow
> than it otherwise would be.

Good point; will split.