On Mon, Nov 19, 2018 at 10:40:53AM -0500, Derrick Stolee wrote:
> > 2fa233a554 builtin/pack-objects.c 1512) hashcpy(base_oid.hash,
> > base_sha1);
> > 2fa233a554 builtin/pack-objects.c 1513) if
> > (!in_same_island(&delta->idx.oid, &base_oid))
> > 2fa233a554 builtin/pack-objects.c 1514) return 0;
>
> These lines are inside a block for the following if statement:
>
> + /*
> + * Otherwise, reachability bitmaps may tell us if the receiver has
> it,
> + * even if it was buried too deep in history to make it into the
> + * packing list.
> + */
> + if (thin && bitmap_has_sha1_in_uninteresting(bitmap_git, base_sha1))
> {
>
> Peff: is this difficult to test?
A bit.
The two features (thin-packs and delta-islands) would not generally be
used together (one is for serving fetches, the other is for optimizing
on-disk packs to serve fetches). Something like:
echo HEAD^ | git pack-objects --revs --thin --delta-islands
would probably exercise it (assuming there's a delta in HEAD^ against
something in HEAD), but you'd need to construct a very specific scenario
if you wanted to do any kind of checks no the output.
> > 28b8a73080 builtin/pack-objects.c 2793) depth++;
> > 108f530385 builtin/pack-objects.c 2797) oe_set_tree_depth(&to_pack, ent,
> > depth);
>
> This 'depth' variable is incremented as part of a for loop in this patch:
>
> static void show_object(struct object *obj, const char *name, void *data)
> @@ -2686,6 +2706,19 @@ static void show_object(struct object *obj, const
> char *name, void *data)
> add_preferred_base_object(name);
> add_object_entry(&obj->oid, obj->type, name, 0);
> obj->flags |= OBJECT_ADDED;
> +
> + if (use_delta_islands) {
> + const char *p;
> + unsigned depth = 0;
> + struct object_entry *ent;
> +
> + for (p = strchr(name, '/'); p; p = strchr(p + 1, '/'))
> + depth++;
> +
> + ent = packlist_find(&to_pack, obj->oid.hash, NULL);
> + if (ent && depth > ent->tree_depth)
> + ent->tree_depth = depth;
> + }
> }
>
> And that 'ent->tree_depth = depth;' line is replaced with the
> oe_set_tree_depth() call in the report.
>
> Since depth is never incremented, we are not covering this block. Is it
> possible to test?
Looks like t5320 only has single-level trees. We probably just need to
add a deeper tree. A more interesting case is when an object really is
found at multiple depths, but constructing a case that cared about that
would be quite complicated.
That said, there is much bigger problem with this code, which is that
108f530385 (pack-objects: move tree_depth into 'struct packing_data',
2018-08-16) is totally broken. It works on the trivial repository in the
test, but try this (especially under valgrind or ASan) on a real
repository:
git repack -adi
which will crash immediately. It doesn't correctly maintain the
invariant that if tree_depth is not NULL, it is the same size as
the main object array.
I'll see if I can come up with a fix.
-Peff
