odb: drop `alternates_db` field

The `struct object_database::alternates_db` field tracks the value of
the "GIT_ALTERNATE_OBJECT_DIRECTORIES" environment variable and is
used in `odb_prepare_alternates()`. It's not necessary to store it as a
separate field anymore though, as we stopped lazy-loading alternates.
Consequently, we can simply pass it to `odb_prepare_alternates()` via
`odb_new()` now.

Do so and remove the field.

Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

0 files changed, 0 insertions, 0 deletions