Re: [PATCH v5 0/9] odb: write alternates at creation time

On Thu, Sep 10, 2026 at 12:53:21PM -0700, Karthik Nayak wrote:

Patrick Steinhardt [off-list ref] writes:

quoted

Hi,

writing alternates into the object database currently happens via
`odb_source_write_alternate()`. But while that creates the ability to
create alternates at arbitrary points of a source's lifetime, we don't
use that functionality in the first place. Instead, we only ever write
alternates when creating a new repository.

This design is suboptimal due to a couple of reasons:

  - It requires us to have a `write_alternates()` callback, which is
    overblown as we never even write alternates to an object database
    after it has been created.

  - We're about to make alternates an implementation detail of the
    object database's backend in a future patch series, so alternate
    implementations may not even support them.

  - The backend has more flexibility with how exactly alternates are
    configured when it itself is in full control over their setup at the
    time where it creates the object database itself.

This patch series thus refactors how we handle alternates so that we
don't write them ad-hoc anymore. Instead, the series introduces a new
option for `odb_source_create_on_disk()` that makes it handle those
alternates at creation time.

This is part of the bigger goal of moving handling of alternates into
the "files" backend.

This series is built on top of 2c3adbb2c4 (The 18th batch, 2026-08-24)
with ps/odb-eagerly-load-alternates at 0076dc9f81 (odb: drop
`alternates_db` field, 2026-08-17) merged into it.

Changes in v5:
  - Rename `add_one_alternate` and `add_one_alternate_data` to
    `collect_one_alternate` and `collect_alternates_data` to clarify
    their intent a bit.
  - Drop extra parameter in `collect_alternates()`.
  - Clarify why we compute `commondir` even though it's unused.
  - Link to v4: https://patch.msgid.link/20260909-pks-odb-write-alternates-at-creation-time-v4-0-d8a78ffc32e4@pks.im

Looks like you missed my comment/question in
CAOLa=ZQaPstiQmXm9=TyWPUxL6X2=Lcqeg6y2XeXzSJDpq-GBA@mail.gmail.com, but
otherwise looks good :)

Oh, indeed, I somehow overlooked that mail. Replied to it now, but I
don't think it requires further changes. Thanks!

Patrick