Fix a leak in code added in c51f8f94e5b (submodule--helper: run update
procedures from C, 2021-08-24), we clobber the "displaypath" member of
the passed-in "struct update_data" both so that die() messages in this
update_submodule() function itself can use it, and for the
run_update_procedure() called within this function.

Signed-off-by: Ævar Arnfjörð Bjarmason <redacted>
---
 builtin/submodule--helper.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/builtin/submodule--helper.c b/builtin/submodule--helper.c
index b65665105e7..4e70a74357c 100644
--- a/builtin/submodule--helper.c
+++ b/builtin/submodule--helper.c

@@ -2551,10 +2551,11 @@ static int update_submodule(struct update_data *update_data,
 			    int *must_die_on_failure)
 {
 	int ret = 1;
+	char *to_free, *restore = update_data->displaypath;
 
 	ensure_core_worktree(update_data->sm_path);
 
-	update_data->displaypath = get_submodule_displaypath(
+	update_data->displaypath = to_free = get_submodule_displaypath(
 		update_data->sm_path, update_data->prefix);

 	determine_submodule_update_strategy(the_repository, update_data->just_cloned,

@@ -2628,6 +2629,9 @@ static int update_submodule(struct update_data *update_data,
 
 	ret = 0;
 cleanup:
+	free(to_free);
+	update_data->displaypath = restore;
+
 	return ret;
 }