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

From: Jonathan Tan <[email-masked]>
Date: Thu, 20 Jan 2022 10:55:48 -0800

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]/
---
 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 &&
-- 
2.34.1.703.g22d0c6ccf7-goog