Add extern function to initialize submodule update options.

include/git2/submodule.h

@@ -110,9 +110,10 @@ typedef enum {
 /**
  * Submodule update options structure
  *
- * Use the GIT_SUBMODULE_UPDATE_OPTIONS_INIT to get the default settings, like this:
+ * Use the GIT_SUBMODULE_UPDATE_OPTIONS_INIT to get the default settings,
+ * like this:
  *
- *		git_submodule_update_options opts = GIT_SUBMODULE_UPDATE_OPTIONS_INIT;
+ * git_submodule_update_options opts = GIT_SUBMODULE_UPDATE_OPTIONS_INIT;
  */
 typedef struct git_submodule_update_options {
 	unsigned int version;
@@ -149,7 +150,21 @@ typedef struct git_submodule_update_options {
 } git_submodule_update_options;
 
 #define GIT_SUBMODULE_UPDATE_OPTIONS_VERSION 1
-#define GIT_SUBMODULE_UPDATE_OPTIONS_INIT {GIT_CHECKOUT_OPTIONS_VERSION, {GIT_CHECKOUT_OPTIONS_VERSION, GIT_CHECKOUT_SAFE}, GIT_REMOTE_CALLBACKS_INIT, GIT_CHECKOUT_SAFE_CREATE}
+#define GIT_SUBMODULE_UPDATE_OPTIONS_INIT \
+	{ GIT_CHECKOUT_OPTIONS_VERSION, \
+		{ GIT_CHECKOUT_OPTIONS_VERSION, GIT_CHECKOUT_SAFE}, \
+	GIT_REMOTE_CALLBACKS_INIT, GIT_CHECKOUT_SAFE_CREATE }
+
+/**
+ * Initializes a `git_submodule_update_options` with default values.
+ * Equivalent to creating an instance with GIT_SUBMODULE_UPDATE_OPTIONS_INIT.
+ *
+ * @param opts The `git_submodule_update_options` instance to initialize.
+ * @param version Version of struct; pass `GIT_SUBMODULE_UPDATE_OPTIONS_VERSION`
+ * @return Zero on success; -1 on failure.
+ */
+GIT_EXTERN(int) git_submodule_update_init_options(
+	git_submodule_update_options *opts, unsigned int version);
 
 /**
  * Update a submodule. This will clone a missing submodule and

src/submodule.c

@@ -898,6 +898,13 @@ static int git_submodule_update_repo_init_cb(
 	return submodule_repo_create(out, sm->repo, path);
 }
 
+int git_submodule_update_init_options(git_submodule_update_options *opts, unsigned int version)
+{
+	GIT_INIT_STRUCTURE_FROM_TEMPLATE(
+		opts, version, git_submodule_update_options, GIT_SUBMODULE_UPDATE_OPTIONS_INIT);
+	return 0;
+}
+
 int git_submodule_update(git_submodule *sm, int init, git_submodule_update_options *_update_options)
 {
 	int error;

tests/structinit/structinit.c

@@ -125,4 +125,9 @@ void test_structinit_structinit__compare(void)
 	CHECK_MACRO_FUNC_INIT_EQUAL( \
 		git_refdb_backend, GIT_REFDB_BACKEND_VERSION, \
 		GIT_REFDB_BACKEND_INIT, git_refdb_init_backend);
+
+	/* submodule update */
+	CHECK_MACRO_FUNC_INIT_EQUAL( \
+		git_submodule_update_options, GIT_SUBMODULE_UPDATE_OPTIONS_VERSION, \
+		GIT_SUBMODULE_UPDATE_OPTIONS_INIT, git_submodule_update_init_options);
 }