Re: [PATCH 2/3] refs: introduce new API, wrap old API shallowly around new API

[Stefan Beller <sbeller@google.com>]

On Fri, Jul 27, 2018 at 10:19 AM Brandon Williams <bmwill@google.com> wrote:
>
> On 07/27, Duy Nguyen wrote:
> > On Fri, Jul 27, 2018 at 2:40 AM Stefan Beller <sbeller@google.com> wrote:
> > >
> > > Currently the refs API takes a 'ref_store' as an argument to specify
> > > which ref store to iterate over; however it is more useful to specify
> > > the repository instead (or later a specific worktree of a repository).
> >
> > There is no 'later'. worktrees.c already passes a worktree specific
> > ref store. If you make this move you have to also design a way to give
> > a specific ref store now.
> >
> > Frankly I still dislike the decision to pass repo everywhere,
> > especially when refs code already has a nice ref-store abstraction.
> > Some people frown upon back pointers. But I think adding a back
> > pointer in ref-store, pointing back to the repository is the right
> > move.
>
> I don't quite understand why the refs code would need a whole repository
> and not just the ref-store it self.  I thought the refs code was self
> contained enough that all its state was based on the passed in
> ref-store.  If its not, then we've done a terrible job at avoiding
> layering violations (well actually we're really really bad at this in
> general, and I *think* we're trying to make this better though the
> object store/index refactoring).
>
> If anything I would expect that the actual ref-store code would remain
> untouched by any refactoring and that instead the higher-level API that
> hasn't already been converted to explicitly use a ref-store (and instead
> just calls the underlying impl with get_main_ref_store()).  Am I missing
> something here?

Then I think we might want to go with the original in Stolees proposal
https://github.com/gitgitgadget/git/pull/11/commits/300db80140dacc927db0d46c804ca0ef4dcc1be1
but there the call to for_each_replace_ref just looks ugly, as it takes the
repository as both the repository where to obtain the ref store from
as well as the back pointer.

I anticipate that we need to have a lot of back pointers to the repository
in question, hence I think we should have the repository pointer promoted
to not just a back pointer.