[PATCH v3] stash: avoid recursive hard reset on submodules

[Jakob Jarmar <jakob.j@gmail.com>]

git stash push does not recursively stash submodules, but if
submodule.recurse is set, it may recursively reset --hard them. Having
only the destructive action recurse is likely to be surprising
behaviour, and unlikely to be desirable, so the easiest fix should be to
ensure that the call to git reset --hard never recurses into submodules.

This matches the behavior of check_changes_tracked_files, which ignores
submodules.

Signed-off-by: Jakob Jarmar <jakob@jarmar.se>
---

Notes:
    I went for two separate tests with the same basic setup, one that does
    push + pop (which should be valid regardless of future changes), and one
    that just does push before checking that the submodule still is dirty
    (which would become invalid if git stash were to learn --recurse-submodules
    in the future, but matches this approach).

 builtin/stash.c            |  2 +-
 git-legacy-stash.sh        |  2 +-
 t/t3906-stash-submodule.sh | 42 +++++++++++++++++++++++++++++++++++++-
 3 files changed, 43 insertions(+), 3 deletions(-)

diff --git a/builtin/stash.c b/builtin/stash.c
index b5a301f24d..c986c258f2 100644
--- a/builtin/stash.c
+++ b/builtin/stash.c
@@ -1383,7 +1383,7 @@ static int do_push_stash(const struct pathspec *ps, const char *stash_msg, int q
 			struct child_process cp = CHILD_PROCESS_INIT;
 			cp.git_cmd = 1;
 			argv_array_pushl(&cp.args, "reset", "--hard", "-q",
-					 NULL);
+					 "--no-recurse-submodules", NULL);
 			if (run_command(&cp)) {
 				ret = -1;
 				goto done;
diff --git a/git-legacy-stash.sh b/git-legacy-stash.sh
index f60e9b3e87..07ad4a5459 100755
--- a/git-legacy-stash.sh
+++ b/git-legacy-stash.sh
@@ -370,7 +370,7 @@ push_stash () {
 			git diff-index -p --cached --binary HEAD -- "$@" |
 			git apply --index -R
 		else
-			git reset --hard -q
+			git reset --hard -q --no-recurse-submodules
 		fi
 
 		if test "$keep_index" = "t" && test -n "$i_tree"
diff --git a/t/t3906-stash-submodule.sh b/t/t3906-stash-submodule.sh
index d7219d6f8f..83106fa958 100755
--- a/t/t3906-stash-submodule.sh
+++ b/t/t3906-stash-submodule.sh
@@ -1,6 +1,6 @@
 #!/bin/sh
 
-test_description='stash apply can handle submodules'
+test_description='stash can handle submodules'
 
 . ./test-lib.sh
 . "$TEST_DIRECTORY"/lib-submodule-update.sh
@@ -21,4 +21,44 @@ KNOWN_FAILURE_CHERRY_PICK_SEES_EMPTY_COMMIT=1
 KNOWN_FAILURE_NOFF_MERGE_DOESNT_CREATE_EMPTY_SUBMODULE_DIR=1
 test_submodule_switch "git_stash"
 
+setup_basic() {
+	git init sub &&
+	(
+		cd sub &&
+		test_commit sub_file
+	) &&
+	git init main &&
+	(
+		cd main &&
+		git submodule add ../sub &&
+		test_commit main_file
+	) &&
+	test_when_finished "rm -rf main sub"
+}
+
+test_expect_success 'stash push with submodule.recurse=true preserves dirty submodule worktree' '
+	setup_basic &&
+	(
+		cd main &&
+		git config submodule.recurse true &&
+		echo "x" >main_file.t &&
+		echo "y" >sub/sub_file.t &&
+		git stash push &&
+		test_must_fail git -C sub diff --quiet
+	)
+'
+
+test_expect_success 'stash push and pop with submodule.recurse=true preserves dirty submodule worktree' '
+	setup_basic &&
+	(
+		cd main &&
+		git config submodule.recurse true &&
+		echo "x" >main_file.t &&
+		echo "y" >sub/sub_file.t &&
+		git stash push &&
+		git stash pop &&
+		test_must_fail git -C sub diff --quiet
+	)
+'
+
 test_done
-- 
2.23.0