Re: [PATCH 0/5] Store submodules in a hash, not a linked list

> I have mentioned this patch series on the mailing list a couple of
> time [1,2] but haven't submitted it before. I just rebased it to
> current master. It is available from my Git fork [3] as branch
> "submodule-hash".
> 
> The first point of this patch series is to optimize submodule
> `ref_store` lookup by storing the `ref_store`s in a hashmap rather
> than a linked list. But a more interesting second point is to weaken
> the 1:1 relationship between submodules and `ref_stores` a little bit
> more.

> A `files_ref_store` would be perfectly happy to represent, say, the
> references *physically* stored in a linked worktree (e.g., `HEAD`,
> `refs/bisect/*`, etc) even though that is not the complete collection
> of refs that are *logically* visible from that worktree (which
> includes references from the main repository, too). But the old code
> was confusing the two things by storing "submodule" in every
> `ref_store` instance.
> 
> So push the submodule attribute down to the `files_ref_store` class
> (but continue to let the `ref_store`s be looked up by submodule).