add note go ODB initialization in preparation for dealing with many s…

…mall packs.

When fetching, currently each of these creates a possibly small pack.
We can tackle this in many areas, so ideally there is a best algorithm
for this, maybe it is indeed just recency, or there is a selection.
Have to figure that out.

Further, small packs should be exploded, using `fetch.unpackLimit`.

gix-odb/src/store_impls/dynamic/load_index.rs

@@ -493,6 +493,11 @@ impl super::Store {
         // Unlike libgit2, do not sort by modification date, but by size and put the biggest indices first. That way
         // the chance to hit an object should be higher. We leave it to the handle to sort by LRU.
         // Git itself doesn't change the order which may safe time, but we want it to be stable which also helps some tests.
+        // NOTE: this will work well for well-packed repos or those using geometric repacking, but force us to open a lot
+        //       of files when dealing with new objects, as there is no notion of recency here as would be with unmaintained
+        //       repositories. Different algorithms should be provided, like newest packs first, and possibly a mix of both
+        //       with big packs first, then sorting by recency for smaller packs.
+        //       We also want to implement `fetch.unpackLimit` to alleviate this issue a little.
         indices_by_modification_time.sort_by(|l, r| l.2.cmp(&r.2).reverse());
         Ok(indices_by_modification_time)
     }