Re: [PATCH v4 3/4] submodule: support running in multiple worktree setup

[Stefan Beller <sbeller@google.com>]

On Fri, Jul 22, 2016 at 10:09 AM, Duy Nguyen <pclouds@gmail.com> wrote:
>
> I just quickly glanced through the rest of this mail because, as a
> submodule ignorant, it's just mumbo jumbo to me. But what I see here
> is, there may be problems if we choose to share some submodule info,
> but I haven't seen any good thing from sharing any submodule info at
> all.

Okay. :(

I assume the sharing is beneficial. (As a work-tree ignorant) I thought
we had this main work tree, which also holds the repository, whereas
the other working trees have a light weight implementation (e.g. just
a .git file pointing back to the main working tree/git dir).

So in a way my mental model is more like the config sharing here:
You can configure things in ~/.gitconfig for example that have effects
on more than one repo. Similarly you would want to configure things
in one repo, that has effect on more than one working tree?

And my assumption was to have the repository specific parts be shared,
whereas the working tree specific things should not be shared.

By working tree specific I strongly mean:

* existence in the working tree
* the checked out sha1
* submodule.$name.path

By repository specific I strongly mean:

* the submodule URL

I am not sure about:

* submodule.$name.update, submodule.$name.ignore,
   submodule.$name.branch,
  These have to be able to be different across working trees, but do we
  require them to be set for each working tree individually?  I thought a
  repo wide setup with defaults may be ok?

>
> I can imagine long term you may want to just clone a submodule repo
> once and share it across worktrees that use it, so maybe it's just me
> not seeing things and this may be a step towards that.

Just as Junio put it:
> I agree that when a top-level superproject has multiple worktrees
> these multiple worktrees may want to have the same submodule in
> different states, but I'd imagine that they want to share the same
> physical repository (i.e. $GIT_DIR/modules/$name of the primary
> worktree of the superproject)---is everybody involved in the
> discussion share this assumption?

I agree with that as well.

>
> Anyway, I assume some people will be working on the submodule side.

Once the discussion comes to a rough agreement, I'll give it a shot.

> And because I have not heard any bad thing about the new config
> design, I'm going to drop submodule patches from this series and focus
> on polishing config stuff.

Oh, sorry for not focusing on that part. The design of git config --worktree
is sound IMO.

> --
> Duy