Ævar Arnfjörð Bjarmason [off-list ref] writes:

quoted

quoted

[...]
This is still in this series as 02/12. I think you've misunderstood
that code, it *is* invoking "git submodule--helper" with
"--super-prefix", but the option is passed as:

    git --super-prefix <path> submodule--helper

And not as:

    git submodule--helper --super-prefix <path>

This is thus handled by other code before builtin/submodule--helper.c,
and it doesn't need to handle it.

But anyway, this is confusing, so I updated the commit message (seen
in the range-diff below)>

Ah that's right, I forgot that we have to pass it to "git" directly.
Thanks.

I wonder why we ever needed this. 89c8626557 (submodule helper: support
super prefix, 2016-12-08) doesn't really explain it, so it looks like
I'll have to dig around the ML.

It was needed, but not after b3c5f5cb048 (submodule: move core
cmd_update() logic to C, 2022-03-15) as my 02/12 discusses.

As a quick test try to check out b3c5f5cb048 and apply this change:

    -#define SUPPORT_SUPER_PREFIX (1<<0)
    +#define SUPPORT_SUPER_PREFIX 0

You'll find that t7406-submodule-update.sh passes, but check out its
parent (which is a commit of yours) and it'll fail, as we'll then emit
output like:

    -Submodule path '../super': checked out 'e1c658656b91df52a4634fbffeaa739807ce3521'
    +Submodule path 'super': checked out 'e1c658656b91df52a4634fbffeaa739807ce3521'

So this is just one of the things that were overly complex in
git-submodule--helper because parts of it had to bridge the gap between
*.sh and *.c land, but once we moved more parts to C we ended up getting
that for free.

Ah yes you are right, as of b3c5f5cb048 we never pass `--super-prefix`
to "git submodule" any more. Great!

I also remember that when I was reading the patch that became
b3c5f5cb048 (submodule: move core cmd_update() logic to C, 2022-03-15),
I noted (internally) that we used `prefix` to set "--recursive-prefix",
which was unusual because `prefix` is usually mapped to
"--super-prefix".

I have a patch to replace "--recursive-prefix" with "--super-prefix",
but it doesn't make sense for that patch to be included in this series
(it's preparation for something else entirely, and it won't make this
series any cleaner.)