options: make --h list options according to a pattern passed to it

Useless feature, but I want it.

Won't work on Windows due to missing fnmatch().

options/m_config.c

@@ -29,6 +29,11 @@
 #include <stdbool.h>
 #include <pthread.h>
 
+#define HAVE_FNMATCH HAVE_POSIX
+#if HAVE_FNMATCH
+#include <fnmatch.h>
+#endif
+
 #include "libmpv/client.h"
 
 #include "mpv_talloc.h"
@@ -41,6 +46,8 @@
 #include "misc/node.h"
 #include "osdep/atomic.h"
 
+extern const char mp_help_text[];
+
 static const union m_option_value default_value;
 
 // Profiles allow to predefine some sets of options that can then
@@ -171,9 +178,13 @@ static int show_profile(struct m_config *config, bstr param)
     return M_OPT_EXIT - 1;
 }
 
-static int list_options(struct m_config *config)
+static int list_options(struct m_config *config, bstr val, bool show_help)
 {
-    m_config_print_option_list(config);
+    char s[100];
+    snprintf(s, sizeof(s), "%.*s", BSTR_P(val));
+    if (show_help)
+        mp_info(config->log, "%s", mp_help_text);
+    m_config_print_option_list(config, s);
     return M_OPT_EXIT;
 }
 
@@ -762,8 +773,10 @@ static int m_config_parse_option(struct m_config *config, struct bstr name,
         return parse_profile(config, co->opt, name, param, set, flags);
     if (config->use_profiles && bstr_equals0(name, "show-profile"))
         return show_profile(config, param);
+    if (bstr_equals0(name, "h") || bstr_equals0(name, "help"))
+        return list_options(config, param, true);
     if (bstr_equals0(name, "list-options"))
-        return list_options(config);
+        return list_options(config, (bstr){0}, false);
 
     // Option with children are a bit different to parse
     if (co->opt->type->flags & M_OPT_TYPE_HAS_CHILD) {
@@ -914,7 +927,7 @@ static int sort_opt_compare(const void *pa, const void *pb)
     return strcasecmp(a->name, b->name);
 }
 
-void m_config_print_option_list(const struct m_config *config)
+void m_config_print_option_list(const struct m_config *config, const char *name)
 {
     char min[50], max[50];
     int count = 0;
@@ -933,6 +946,10 @@ void m_config_print_option_list(const struct m_config *config)
             continue;
         if (co->is_hidden)
             continue;
+#if HAVE_FNMATCH
+        if (fnmatch(name, co->name, 0))
+            continue;
+#endif
         MP_INFO(config, " %s%-30s", prefix, co->name);
         if (opt->type == &m_option_type_choice) {
             MP_INFO(config, " Choices:");

options/m_config.h

@@ -212,10 +212,7 @@ bool m_config_is_in_group(struct m_config *config,
 // Return all (visible) option names as NULL terminated string list.
 char **m_config_list_options(void *ta_parent, const struct m_config *config);
 
-/*  Print a list of all registered options.
- *  \param config The config object.
- */
-void m_config_print_option_list(const struct m_config *config);
+void m_config_print_option_list(const struct m_config *config, const char *name);
 
 
 /*  Find the profile with the given name.

options/m_option.c

@@ -2771,7 +2771,7 @@ print_help: ;
     if (config) {
         if (desc->print_help)
             desc->print_help(log);
-        m_config_print_option_list(config);
+        m_config_print_option_list(config, "");
     } else {
         mp_warn(log, "Option %.*s: item %.*s doesn't exist.\n",
                BSTR_P(opt_name), BSTR_P(name));