Re: [PATCH v3 2/4] introduce submodule.superprojectGitDir record

From: Derrick Stolee <stolee@gmail.com>
To: Emily Shaffer <emilyshaffer@google.com>, git@vger.kernel.org
Cc: Junio C Hamano <gitster@pobox.com>
Subject: Re: [PATCH v3 2/4] introduce submodule.superprojectGitDir record
Date: Thu, 19 Aug 2021 20:38:19 -0400	[thread overview]
Message-ID: <9fecf160-9646-7e56-478c-aa5f8defa6a9@gmail.com> (raw)
In-Reply-To: <20210819200953.2105230-3-emilyshaffer@google.com>

On 8/19/2021 4:09 PM, Emily Shaffer wrote:
...
> +submodule.superprojectGitDir::
> +	The relative path from the submodule's worktree to its superproject's
> +	gitdir. When Git is run in a repository, it usually makes no difference
> +	whether this repository is standalone or a submodule, but if this
> +	configuration variable is present, additional behavior may be possible,
> +	such as "git status" printing additional information about this
> +	submodule's status with respect to its superproject. This config should
> +	only be present in projects which are submodules, but is not guaranteed
> +	to be present in every submodule, so only optional value-added behavior
> +	should be linked to it. It is set automatically during
> +	submodule creation.
> ++
> +	Because of this configuration variable, it is forbidden to use the
> +	same submodule worktree shared by multiple superprojects.

nit: this paragraph linked with the "+" line should have no tabbing.

Also, could we use the same submodule worktree for multiple superprojects
_before_ this configuration variable? That seems wild to me. Or, is that
not a new requirement?

Perhaps you mean something like this instead:

	It is forbidden to use the same submodule worktree for multiple
	superprojects, so this configuration variable stores the unique
	superproject and is not multi-valued.

> diff --git a/builtin/submodule--helper.c b/builtin/submodule--helper.c
> index d55f6262e9..d60fcd2c7d 100644
> --- a/builtin/submodule--helper.c
> +++ b/builtin/submodule--helper.c
> @@ -1910,6 +1910,10 @@ static int module_clone(int argc, const char **argv, const char *prefix)
>  		git_config_set_in_file(p, "submodule.alternateErrorStrategy",
>  					   error_strategy);
>  
> +	git_config_set_in_file(p, "submodule.superprojectGitdir",
> +			       relative_path(absolute_path(get_git_dir()),
> +					     path, &sb));
> +

I see that all new submodules will have this configuration set. But we will
also live in a world where some existing submodules do not have this variable
set. I'll look elsewhere for compatibility checks.

>  inspect() {
> -	dir=$1 &&
> -
> -	git -C "$dir" for-each-ref --format='%(refname)' 'refs/heads/*' >heads &&
> -	{ git -C "$dir" symbolic-ref HEAD || :; } >head &&
> -	git -C "$dir" rev-parse HEAD >head-sha1 &&
> -	git -C "$dir" update-index --refresh &&
> -	git -C "$dir" diff-files --exit-code &&
> -	git -C "$dir" clean -n -d -x >untracked
> +	sub_dir=$1 &&
> +	super_dir=$2 &&
> +
> +	git -C "$sub_dir" for-each-ref --format='%(refname)' 'refs/heads/*' >heads &&
> +	{ git -C "$sub_dir" symbolic-ref HEAD || :; } >head &&
> +	git -C "$sub_dir" rev-parse HEAD >head-sha1 &&
> +	git -C "$sub_dir" update-index --refresh &&
> +	git -C "$sub_dir" diff-files --exit-code &&
> +	cached_super_dir="$(git -C "$sub_dir" config --get submodule.superprojectGitDir)" &&
> +	[ "$(git -C "$super_dir" rev-parse --absolute-git-dir)" \
> +		-ef "$sub_dir/$cached_super_dir" ] &&
> +	git -C "$sub_dir" clean -n -d -x >untracked

You rewrote this test in the previous patch, and now every line is changed
because you renamed 'dir' to 'sub_dir'. Could the previous patch use
'sub_dir' from the start so this change only shows the new lines instead of
many edited lines?

>  }
>  
>  test_expect_success 'submodule add' '
> @@ -138,7 +142,7 @@ test_expect_success 'submodule add' '
>  	) &&
>  
>  	rm -f heads head untracked &&
> -	inspect addtest/submod &&
> +	inspect addtest/submod addtest &&

Similarly, I would not be upset to see these lines be changed just the
once, even if the second argument is ignored for a single commit. But
this nitpick is definitely less important since I could see taste
swaying things either way.

Thanks,
-Stolee