submodule--helper: free rest of "displaypath" in "struct update_data"

Fix a leak in code added in c51f8f9 (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.

Fix a leak in code added in 51f8f94e5b (submodule--helper: run update
procedures from C, 2021-08-24). We'd always clobber the old
"displaypath" member of the previously passed-in "struct update_data".

A better fix for this would be to remove the "displaypath" member from
the "struct update_data" entirely. Along with "oid", "suboid",
"just_cloned" and "sm_path" it's managing members that mainly need to
be passed between 1-3 stack frames of functions adjacent to this
code. But doing so would be a much larger change (I have it locally,
and fully untangling that in an incremental way is a 10 patch
journey).

So let's go for this much more isolated fix suggested by Glen. We
FREE_AND_NULL() the "update_data->displaypath", the "AND_NULL()" part
of that is needed due to the later "free(ud->displaypath)" in
"update_data_release()" introduced in the preceding commit

Moving ensure_core_worktree() out of update_submodule() may not be
strictly required, but in doing so we are left with the exact same
ordering as before, making this a smaller functional change.

Helped-by: Glen Choo <[email protected]>
Signed-off-by: Ævar Arnfjörð Bjarmason <[email protected]>
Reviewed-by: Glen Choo <[email protected]>
Signed-off-by: Junio C Hamano <[email protected]>

Author: avar

builtin/submodule--helper.c

@@ -2484,13 +2484,6 @@ static int update_submodule(struct update_data *update_data)
 {
 	int ret;
 
-	ret = ensure_core_worktree(update_data->sm_path);
-	if (ret)
-		return ret;
-
-	update_data->displaypath = get_submodule_displaypath(
-		update_data->sm_path, update_data->prefix);
-
 	ret = determine_submodule_update_strategy(the_repository,
 						  update_data->just_cloned,
 						  update_data->sm_path,
@@ -2596,7 +2589,15 @@ static int update_submodules(struct update_data *update_data)
 		update_data->just_cloned = ucd.just_cloned;
 		update_data->sm_path = ucd.sub->path;
 
+		code = ensure_core_worktree(update_data->sm_path);
+		if (code)
+			goto fail;
+
+		update_data->displaypath = get_submodule_displaypath(
+			update_data->sm_path, update_data->prefix);
 		code = update_submodule(update_data);
+		FREE_AND_NULL(update_data->displaypath);
+fail:
 		if (!code)
 			continue;
 		ret = code;