Re: [PATCH v4 7/7] submodule: move core cmd_update() logic to C

> From: Atharva Raykar <raykar.ath@gmail.com>
>
> This patch completes the conversion past the flag parsing of
> `submodule update` by introducing a helper subcommand called
> `submodule--helper update`. The behaviour of `submodule update` should
> remain the same after this patch.
>
> We add more fields to the `struct update_data` that are required by
> `struct submodule_update_clone` to be able to perform a clone, when that
> is needed to be done.
>
> Recursing on a submodule is done by calling a subprocess that launches
> `submodule--helper update`, with a modified `--recursive-prefix` and
> `--prefix` parameter.
>
> We also introduce `update_submodules2()` and `update_submodule2()`
> which will supersede `update_submodules()` and `update_submodule()`.
>
> When the `--init` flag is passed to the subcommand, we do not spawn a
> new subprocess and call `submodule--helper init` on the submodule paths,
> because the Git machinery is not able to pick up the configuration
> changes introduced by that init call[1]. So we instead run the
> `init_submodule_cb()` callback over each submodule in the same process.
>
> While we are at it, we also remove the fetch_in_submodule() shell
> function since it is no longer used anywhere.
>
> [1] https://lore.kernel.org/git/CAP8UFD0NCQ5w_3GtT_xHr35i7h8BuLX4UcHNY6VHPGREmDVObA@mail.gmail.com/
>
> Mentored-by: Christian Couder <christian.couder@gmail.com>
> Mentored-by: Shourya Shukla <periperidip@gmail.com>
> Signed-off-by: Atharva Raykar <raykar.ath@gmail.com>
> Signed-off-by: Junio C Hamano <gitster@pobox.com>
> Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
> ---