The sparse-checkout builtin has not changed
the way these features interact, but we may as well document it in
the builtin docs.

Using 'git submodule (init|deinit)' a user can select a subset of
submodules to populate. This behaves very similar to the sparse-checkout
feature, but those directories contain their own .git directory
including an object database and ref space. To have the sparse-checkout
file also determine if those files should exist would easily cause
problems. Therefore, keeping these features independent in this way
is the best way forward.

Also create a test that demonstrates this behavior to make sure
it doesn't change as the sparse-checkout feature evolves.

Reported-by: Junio C Hamano <redacted>
Signed-off-by: Derrick Stolee <redacted>
---
 Documentation/git-sparse-checkout.txt | 10 ++++++++++
 t/t1091-sparse-checkout-builtin.sh    | 28 +++++++++++++++++++++++++++
 2 files changed, 38 insertions(+)

diff --git a/Documentation/git-sparse-checkout.txt b/Documentation/git-sparse-checkout.txt
index dcca9ee826..2b7aaa0310 100644
--- a/Documentation/git-sparse-checkout.txt
+++ b/Documentation/git-sparse-checkout.txt

@@ -164,6 +164,16 @@ case-insensitive check. This corrects for case mismatched filenames in the
 'git sparse-checkout set' command to reflect the expected cone in the working
 directory.

+
+SUBMODULES
+----------
+
+If your repository contains one or more submodules, then those submodules will
+appear based on which you initialized with the `git submodule` command. If
+your sparse-checkout patterns exclude an initialized submodule, then that
+submodule will still appear in your working directory.
+
+
 SEE ALSO
 --------

diff --git a/t/t1091-sparse-checkout-builtin.sh b/t/t1091-sparse-checkout-builtin.sh
index 37f6d8fa90..5572beeeca 100755
--- a/t/t1091-sparse-checkout-builtin.sh
+++ b/t/t1091-sparse-checkout-builtin.sh

@@ -340,4 +340,32 @@ test_expect_success 'cone mode: set with core.ignoreCase=true' '
        test_cmp expect dir
 '

+test_expect_success 'interaction with submodules' '
+       git clone repo super &&
+       (
+               cd super &&
+               mkdir modules &&
+               git submodule add ../repo modules/child &&
+               git add . &&
+               git commit -m "add submodule" &&
+               git sparse-checkout init --cone &&
+               git sparse-checkout set folder1
+       ) &&
+       list_files super >dir &&
+       cat >expect <<-EOF &&
+               a
+               folder1
+               modules
+       EOF
+       test_cmp expect dir &&
+       list_files super/modules/child >dir &&
+       cat >expect <<-EOF &&
+               a
+               deep
+               folder1
+               folder2
+       EOF
+       test_cmp expect dir
+'
+
 test_done
--