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

On Fri, Nov 05, 2021 at 09:51:12AM +0100, Ævar Arnfjörð Bjarmason wrote:

On Thu, Nov 04 2021, Emily Shaffer wrote:

quoted

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 <redacted>
---
 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?

I answered vs. your other mail; yes, it's still needed, and last I
checked Atharva's series had been kicked out to make room for this one.

1. https://lore.kernel.org/git/211105.861r3vhtot.gmgdl@evledraar.gmail.com/ (local)
2. https://lore.kernel.org/git/20211013051805.45662-8-raykar.ath@gmail.com/ (local)
3. https://lore.kernel.org/git/20211013051805.45662-1-raykar.ath@gmail.com/ (local)
4. https://lore.kernel.org/git/YWiXL+plA7GHfuVv@google.com/ (local)