submodule: add a helper to check if it is safe to write to .gitmodules

diff --git a/builtin/submodule--helper.c b/builtin/submodule--helper.c
index a85a6ef438b635dd068d318b16f5512776307bed..8699515e81c26c6e70b3f1de95a35ab118ac3dd6 100644 (file)
--- a/builtin/submodule--helper.c
+++ b/builtin/submodule--helper.c
@@ -2005,6 +2005,28 @@ static int check_name(int argc, const char **argv, const char *prefix)
 
 static int module_config(int argc, const char **argv, const char *prefix)
 {
+       enum {
+               CHECK_WRITEABLE = 1
+       } command = 0;
+
+       struct option module_config_options[] = {
+               OPT_CMDMODE(0, "check-writeable", &command,
+                           N_("check if it is safe to write to the .gitmodules file"),
+                           CHECK_WRITEABLE),
+               OPT_END()
+       };
+       const char *const git_submodule_helper_usage[] = {
+               N_("git submodule--helper config name [value]"),
+               N_("git submodule--helper config --check-writeable"),
+               NULL
+       };
+
+       argc = parse_options(argc, argv, prefix, module_config_options,
+                            git_submodule_helper_usage, PARSE_OPT_KEEP_ARGV0);
+
+       if (argc == 1 && command == CHECK_WRITEABLE)
+               return is_writing_gitmodules_ok() ? 0 : -1;
+
        /* Equivalent to ACTION_GET in builtin/config.c */
        if (argc == 2)
                return print_config_from_gitmodules(the_repository, argv[1]);
@@ -2013,7 +2035,7 @@ static int module_config(int argc, const char **argv, const char *prefix)
        if (argc == 3)
                return config_set_in_gitmodules_file_gently(argv[1], argv[2]);
 
-       die("submodule--helper config takes 1 or 2 arguments: name [value]");
+       usage_with_options(git_submodule_helper_usage, module_config_options);
 }
 
 #define SUPPORT_SUPER_PREFIX (1<<0)