[PATCH v2 24/24] submodule--helper: fix a configure_added_submodule() leak

["Ævar Arnfjörð Bjarmason" <avarab@gmail.com>]

Fix config API a memory leak added in a452128a36c (submodule--helper:
introduce add-config subcommand, 2021-08-06) by using the *_tmp()
variant of git_config_get_string().

In this case we're only checking whether
the (repo|git)_config_get_string() call is telling us that the
"submodule.active" key exists.

As with the preceding commit we'll find many other such patterns in
the codebase if we go fishing. E.g. "git gc" leaks in the code added
in 61f7a383d3b (maintenance: use 'incremental' strategy by default,
2020-10-15). Similar code in "git gc" added in
b08ff1fee00 (maintenance: add --schedule option and config,
2020-09-11) doesn't leak, but we could avoid the malloc() & free() in
that case.

A coccinelle rule to find those would find and fix some leaks, and
cases where we're doing needless malloc() + free()'s but only care
about the key existence, or are copying
the (repo|git)_config_get_string() return value right away.

But as with the preceding commit let's punt on all of that for now,
and just narrowly fix this specific case in submodule--helper.

Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
---
 builtin/submodule--helper.c    | 4 ++--
 t/t7413-submodule-is-active.sh | 1 +
 2 files changed, 3 insertions(+), 2 deletions(-)

diff --git a/builtin/submodule--helper.c b/builtin/submodule--helper.c
index a944f6fa442..09b8a1c2947 100644
--- a/builtin/submodule--helper.c
+++ b/builtin/submodule--helper.c
@@ -3264,7 +3264,7 @@ static int config_submodule_in_gitmodules(const char *name, const char *var, con
 static void configure_added_submodule(struct add_data *add_data)
 {
 	char *key;
-	char *val = NULL;
+	const char *val;
 	struct child_process add_submod = CHILD_PROCESS_INIT;
 	struct child_process add_gitmodules = CHILD_PROCESS_INIT;
 
@@ -3309,7 +3309,7 @@ static void configure_added_submodule(struct add_data *add_data)
 	 * is_submodule_active(), since that function needs to find
 	 * out the value of "submodule.active" again anyway.
 	 */
-	if (!git_config_get_string("submodule.active", &val)) {
+	if (!git_config_get_string_tmp("submodule.active", &val)) {
 		/*
 		 * If the submodule being added isn't already covered by the
 		 * current configured pathspec, set the submodule's active flag
diff --git a/t/t7413-submodule-is-active.sh b/t/t7413-submodule-is-active.sh
index c8e7e983317..c4c1f86f3d2 100755
--- a/t/t7413-submodule-is-active.sh
+++ b/t/t7413-submodule-is-active.sh
@@ -6,6 +6,7 @@ This test verifies that `git submodue--helper is-active` correctly identifies
 submodules which are "active" and interesting to the user.
 '
 
+TEST_PASSES_SANITIZE_LEAK=true
 . ./test-lib.sh
 
 test_expect_success 'setup' '
-- 
2.37.1.1062.g385eac7fccf