Subject: Re: [PATCH v5 4/4] submodule: record superproject gitdir during 'update'

From: Ævar Arnfjörð Bjarmason <[email-masked]>
Date: Fri, 05 Nov 2021 09:51:12 +0100

On Thu, Nov 04 2021, Emily Shaffer wrote:

> A recorded hint path to the superproject's gitdir might be added during
> 'git submodule add', but in some cases - like submodules which were
> created before 'git submodule add' learned to record that info - it might
> be useful to update the hint. Let's do it during 'git submodule
> update', when we already have a handle to the superproject while calling
> operations on the submodules.
>
> Signed-off-by: Emily Shaffer <[email-masked]>
> ---
>  git-submodule.sh            | 14 ++++++++++++++
>  t/t7406-submodule-update.sh | 12 ++++++++++++
>  2 files changed, 26 insertions(+)
>
> diff --git a/git-submodule.sh b/git-submodule.sh
> index 652861aa66..873d64eb99 100755
> --- a/git-submodule.sh
> +++ b/git-submodule.sh
> @@ -449,6 +449,20 @@ cmd_update()
>  			;;
>  		esac
>  
> +		# Cache a pointer to the superproject's common dir. This may have
> +		# changed, unless it's a fresh clone. Writes it to worktree
> +		# if applicable, otherwise to local.
> +		if test -z "$just_cloned"
> +		then
> +			sm_gitdir="$(git -C "$sm_path" rev-parse --absolute-git-dir)"
> +			relative_gitdir="$(git rev-parse --path-format=relative \
> +							 --prefix "${sm_gitdir}" \
> +							 --git-common-dir)"
> +
> +			git -C "$sm_path" config --worktree \
> +				submodule.superprojectgitdir "$relative_gitdir"
> +		fi
> +

Aside from the "is this really needed anymore?" comment on this caching
strategy in general I had in [1] does this really need to be adding new
shell code to git-submodule.sh given that we're actively trying to get
rid of it entirely and move it over to C.

I.e. here we've just called "git submodule--helper
run-update-procedure", and we pass it "$sm_path" (but not "$recursive",
but could easily do so).

It needs to clone this new submodule, so presumably it already has a
"$sm_gitdir" equivalent, and we can turn that into the same relative
path, no?

Can't we call this with a git_config_set*() somewhere in that code?

*investigates a bit*

Okey, so I see that [2] is part of a series that Atharva Raykar had a
version of (including this new git-submodule.sh code above) [3] rebased
on top of an older version of this topic. I.e. this bit is that part of that patch:

+       git_config_set_in_file(config_path, "submodule.superprojectGitdir",
+                              relative_path(get_git_dir(),
+                                            update_data->sm_path, &sb));

I also vaguely recall that Junio ejected his topic to make room for this
topic first.

Maybe I've missed some update on this but is his [2][3] broken in
combination with your topic here? And re[1] is whatever "caching" is
being done here still beneficial once this is all moved to C?

In your [4] there seems to be an agreement to do it the other way
around, but as noted in the mail linked from [1] maybe the caching isn't
needed anymore then?

1. https://lore.kernel.org/git/[email-masked]/
2. https://lore.kernel.org/git/[email-masked]/
3. https://lore.kernel.org/git/[email-masked]/
4. https://lore.kernel.org/git/[email-masked]/