submodule--helper: have --require-init imply --init

Adjust code added in 0060fd1511 (clone --recurse-submodules: prevent
name squatting on Windows, 2019-09-12) to have the internal
--require-init option imply --init, rather than having
"git-submodule.sh" add it implicitly.

This change doesn't make any difference now, but eliminates another
special-case where "git submodule--helper update"'s behavior was
different from "git submodule update". This will make it easier to
eventually replace the cmd_update() function in git-submodule.sh.

We'll still need to keep the distinction between "--init" and
"--require-init" in git-submodule.sh. Once cmd_update() gets
re-implemented in C we'll be able to change variables and other code
related to that, but not yet.

Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

builtin/submodule--helper.c

@@ -2618,7 +2618,7 @@ static int module_update(int argc, const char **argv, const char *prefix)
 		OPT_BOOL(0, "progress", &opt.progress,
 			    N_("force cloning progress")),
 		OPT_BOOL(0, "require-init", &opt.require_init,
-			   N_("disallow cloning into non-empty directory")),
+			   N_("disallow cloning into non-empty directory, implies --init")),
 		OPT_BOOL(0, "single-branch", &opt.single_branch,
 			 N_("clone only one branch, HEAD or --branch")),
 		OPT_PARSE_LIST_OBJECTS_FILTER(&filter_options),
@@ -2642,6 +2642,9 @@ static int module_update(int argc, const char **argv, const char *prefix)
 	argc = parse_options(argc, argv, prefix, module_update_options,
 			     git_submodule_helper_usage, 0);
 
+	if (opt.require_init)
+		opt.init = 1;
+
 	if (filter_options.choice && !opt.init) {
 		usage_with_options(git_submodule_helper_usage,
 				   module_update_options);

git-submodule.sh

@@ -251,7 +251,6 @@ cmd_update()
 			init=1
 			;;
 		--require-init)
-			init=1
 			require_init=1
 			;;
 		--remote)