Subject: Re: [PATCH] sparse-checkout: create leading directory

From: Ævar Arnfjörð Bjarmason <[email-masked]>
Date: Thu, 20 Jan 2022 22:30:03 +0100

On Thu, Jan 20 2022, Jonathan Tan wrote:

> When creating the sparse-checkout file, Git does not create the leading
> directory, "$GIT_DIR/info", if it does not exist. This causes problems
> if the repository does not have that directory. Therefore, ensure that
> the leading directory is created.
>
> This is the only "open" in builtin/sparse-checkout.c that does not have
> a leading directory check. (The other one in write_patterns_and_update()
> does.)
>
> Note that the test needs to explicitly specify a template when running
> "git init" because the default template used in the tests has the
> "info/" directory included.
>
> Signed-off-by: Jonathan Tan <[email-masked]>
> ---
> This problem is being discussed in [1], and we also noticed this problem
> internally at $DAYJOB. Here's a fix.
>
> [1] https://lore.kernel.org/git/[email-masked]/

Thanks. This fix looks good to me.

Looking at my [1] my preliminary analysis there wasn't correct,
i.e. there are other cases where we get the "sparse_filename" that you
don't cover here, but e.g. if you do:

    <your test> &&
    rm -rf .git/info &&
    git sparse-checkout add foo

It looks like it will fail either way, so for those other codepaths we
didn't need to ensure the .git/info.

Still, it would be nice to have the fix test for those cases too,
i.e. how various operations are expected to behave if the user were to
rm -rf .git/info. That'll obviously yield a broken repo, but we should
still try to handle it gracefully.

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

> ---
>  builtin/sparse-checkout.c          | 3 +++
>  t/t1091-sparse-checkout-builtin.sh | 7 +++++++
>  2 files changed, 10 insertions(+)
>
> diff --git a/builtin/sparse-checkout.c b/builtin/sparse-checkout.c
> index 679c107036..2b0e1db2d2 100644
> --- a/builtin/sparse-checkout.c
> +++ b/builtin/sparse-checkout.c
> @@ -471,6 +471,9 @@ static int sparse_checkout_init(int argc, const char **argv)
>  		FILE *fp;
>  
>  		/* assume we are in a fresh repo, but update the sparse-checkout file */
> +		if (safe_create_leading_directories(sparse_filename))
> +			die(_("unable to create leading directories of %s"),
> +			    sparse_filename);
>  		fp = xfopen(sparse_filename, "w");
>  		if (!fp)
>  			die(_("failed to open '%s'"), sparse_filename);
> diff --git a/t/t1091-sparse-checkout-builtin.sh b/t/t1091-sparse-checkout-builtin.sh
> index 42776984fe..dba0737599 100755
> --- a/t/t1091-sparse-checkout-builtin.sh
> +++ b/t/t1091-sparse-checkout-builtin.sh
> @@ -79,6 +79,13 @@ test_expect_success 'git sparse-checkout init' '
>  	check_files repo a
>  '
>  
> +test_expect_success 'git sparse-checkout init in empty repo' '
> +	test_when_finished rm -rf empty-repo blank-template &&
> +	mkdir blank-template &&
> +	git init --template=blank-template empty-repo &&
> +	git -C empty-repo sparse-checkout init
> +'
> +
>  test_expect_success 'git sparse-checkout list after init' '
>  	git -C repo sparse-checkout list >actual &&
>  	cat >expect <<-\EOF &&

You're using an overly verbose way to say "no templates, please". You
can squash this in, i.e. --template= is an explicitly supported way to
do that.

diff --git a/t/t1091-sparse-checkout-builtin.sh b/t/t1091-sparse-checkout-builtin.sh
index dba07375993..1fe741d9cd5 100755
--- a/t/t1091-sparse-checkout-builtin.sh
+++ b/t/t1091-sparse-checkout-builtin.sh
@@ -80,9 +80,8 @@ test_expect_success 'git sparse-checkout init' '
 '
 
 test_expect_success 'git sparse-checkout init in empty repo' '
-	test_when_finished rm -rf empty-repo blank-template &&
-	mkdir blank-template &&
-	git init --template=blank-template empty-repo &&
+	test_when_finished rm -rf empty-repo &&
+	git init --template= empty-repo &&
 	git -C empty-repo sparse-checkout init
 '