Re: [RFC PATCH 1/2] refs: make _advance() check struct repo, not flag

>
> Currently, ref iterators access the object store each time they advance
> if and only if the boolean flag DO_FOR_EACH_INCLUDE_BROKEN is unset.
> (The iterators access the object store because, if
> DO_FOR_EACH_INCLUDE_BROKEN is unset, they need to attempt to resolve
> each ref to determine that it is not broken.)
>
> Also, the object store accessed is always that of the_repository, making
> it impossible to iterate over a submodule's refs without
> DO_FOR_EACH_INCLUDE_BROKEN (unless add_submodule_odb() is used).
>
> As a first step in resolving both these problems, replace the
> DO_FOR_EACH_INCLUDE_BROKEN flag with a struct repository pointer. This
> commit is a mechanical conversion - whenever DO_FOR_EACH_INCLUDE_BROKEN
> is set, a NULL repository (representing access to no object store) is
> used instead, and whenever DO_FOR_EACH_INCLUDE_BROKEN is unset, a
> non-NULL repository (representing access to that repository's object
> store) is used instead. Right now, the locations in which
> non-the_repository support needs to be added are marked with BUG()
> statements - in a future patch, these will be replaced. (NEEDSWORK: in
> this RFC patch set, this has not been done)

> - Making all ref stores not access the object store during their
>   _advance() callbacks, and making ref_iterator_advance() be responsible
>   for checking the object store - thus, simplifying the code in that the
>   logic of checking for the flag (current) or the pointer (after the
>   equivalent of this commit) is only in one place instead of in every
>   ref store's callback. However, the ref stores already make use of this
>   flag for another reason - for determining if refs are resolvable when
>   writing (search for "REF_STORE_ODB"). Thus, I decided to retain each