Re: [RFC PATCH 3/3] grep: don't add submodules to the alternates list

>
> When grepping with --recurse-submodules, the object directory of the
> submodule is added to the in-memory alternates list. This makes git need
> to watch out for more packfiles which might bring bad consequences for
> memory and performance.
>
> Now that raw_object_store is a member of the struct repository, it's
> possible to use the submodules' instances directly, without the need to
> add its odbs to the alternates list. So let's instead pass the subrepo
> down to the threads and replace function calls which use
> the_repository by default for their more general counterparts. Also,
> submodule cleanup must be refactored as calling repo_clear() at the end
> of grep_submodules(), might free the subrepo's resources before threads
> have finished working on it. To do that, let's keep track of the
> workers progress and only call repo_clear() when it's safe to do so.