builtin/submodule--helper: clear child process when not running it

In `runcommand_in_submodule_cb()` we may end up not executing the child
command when `argv` is empty. But we still populate the command with
environment variables and other things, which needs cleanup. This leads
to a memory leak because we do not call `finish_command()`.

Fix this by clearing the child process when we don't execute it.

Signed-off-by: Patrick Steinhardt <[email protected]>
Signed-off-by: Junio C Hamano <[email protected]>

Author: pks-t

builtin/submodule--helper.c

@@ -363,9 +363,13 @@ static void runcommand_in_submodule_cb(const struct cache_entry *list_item,
 	if (!info->quiet)
 		printf(_("Entering '%s'\n"), displaypath);
 
-	if (info->argv[0] && run_command(&cp))
-		die(_("run_command returned non-zero status for %s\n."),
-			displaypath);
+	if (info->argv[0]) {
+		if (run_command(&cp))
+			die(_("run_command returned non-zero status for %s\n."),
+			    displaypath);
+	} else {
+		child_process_clear(&cp);
+	}
 
 	if (info->recursive) {
 		struct child_process cpr = CHILD_PROCESS_INIT;

t/t7407-submodule-foreach.sh

@@ -12,6 +12,7 @@ that are currently checked out.
 GIT_TEST_DEFAULT_INITIAL_BRANCH_NAME=main
 export GIT_TEST_DEFAULT_INITIAL_BRANCH_NAME
 
+TEST_PASSES_SANITIZE_LEAK=true
 . ./test-lib.sh