update submodules: add a config option to determine if submodules are updated

In later patches we introduce the options and flag for commands
that modify the working directory, e.g. git-checkout.

Have a central place to store such settings whether we want to update
a submodule.
Signed-off-by: NStefan Beller <sbeller@google.com>
Signed-off-by: NJunio C Hamano <gitster@pobox.com>

submodule.c

@@ -17,6 +17,7 @@
 #include "worktree.h"
 
 static int config_fetch_recurse_submodules = RECURSE_SUBMODULES_ON_DEMAND;
+static int config_update_recurse_submodules = RECURSE_SUBMODULES_DEFAULT;
 static int parallel_jobs = 1;
 static struct string_list changed_submodule_paths = STRING_LIST_INIT_NODUP;
 static int initialized_fetch_ref_tips;
@@ -542,6 +543,11 @@ void set_config_fetch_recurse_submodules(int value)
 	config_fetch_recurse_submodules = value;
 }
 
+void set_config_update_recurse_submodules(int value)
+{
+	config_update_recurse_submodules = value;
+}
+
 static int has_remote(const char *refname, const struct object_id *oid,
 		      int flags, void *cb_data)
 {

submodule.h

@@ -64,6 +64,7 @@ extern void show_submodule_inline_diff(FILE *f, const char *path,
 		const char *del, const char *add, const char *reset,
 		const struct diff_options *opt);
 extern void set_config_fetch_recurse_submodules(int value);
+extern void set_config_update_recurse_submodules(int value);
 extern void check_for_new_submodule_commits(unsigned char new_sha1[20]);
 extern int fetch_populated_submodules(const struct argv_array *options,
 			       const char *prefix, int command_line_option,