Re: [PATCH 1/9] refs: make _advance() check struct repo, not flag

On Tue, Sep 21, 2021 at 09:51:03AM -0700, Jonathan Tan wrote:

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)

I think your goal here of passing around a repository object is good.
But rolling the meaning of DO_FOR_EACH_INCLUDE_BROKEN into an implicit
"do we have a non-NULL repository" makes things awkward, I think.

As you noticed, we can't get rid of the flags parameter entirely. We
still have DO_FOR_EACH_PER_WORKTREE_ONLY. But I also have a series which
adds another flag which pairs with INCLUDE_BROKEN. Having half of the
logic implicit in the repository pointer and half in a flag would be
weird.

I'll post that series in a moment, but what I'm wondering here is: would
it be that big a deal to just pass the repository object around, and it
is simply not used if INCLUDE_BROKEN is passed?

-Peff