options: minor cleanup to --no-... handling

Most options starting with --no-<name> are automatically translated to
--<name>=no. Make the code slightly nicer by using a flag instead of
explicitly comparing option types. Also fix an issue that made the
option parser print nonsense error messages for if --no-... was used for
options which don't support it.

options/m_config.c

@@ -819,16 +819,16 @@ static struct m_config_option *m_config_mogrify_cli_opt(struct m_config *config,
         return co;
 
     // Turn "--no-foo" into "foo" + set *out_negate.
-    if (!co && bstr_eatstart0(name, "no-")) {
-        co = m_config_get_co(config, *name);
+    bstr no_name = *name;
+    if (!co && bstr_eatstart0(&no_name, "no-")) {
+        co = m_config_get_co(config, no_name);
 
         // Not all choice types have this value - if they don't, then parsing
         // them will simply result in an error. Good enough.
-        if (co && co->opt->type != CONF_TYPE_FLAG &&
-                  co->opt->type != CONF_TYPE_CHOICE &&
-                  co->opt->type != &m_option_type_aspect)
+        if (!co || !(co->opt->type->flags & M_OPT_TYPE_CHOICE))
             return NULL;
 
+        *name = no_name;
         *out_negate = true;
         return co;
     }

options/m_option.c

@@ -183,11 +183,11 @@ const m_option_type_t m_option_type_flag = {
     // need yes or no in config files
     .name  = "Flag",
     .size  = sizeof(int),
-    .flags = M_OPT_TYPE_OPTIONAL_PARAM,
+    .flags = M_OPT_TYPE_OPTIONAL_PARAM | M_OPT_TYPE_CHOICE,
     .parse = parse_flag,
     .print = print_flag,
     .copy  = copy_opt,
-    .add = add_flag,
+    .add   = add_flag,
     .set   = flag_set,
     .get   = flag_get,
 };
@@ -747,6 +747,7 @@ static char *print_choice(const m_option_t *opt, const void *val)
 const struct m_option_type m_option_type_choice = {
     .name  = "Choice",
     .size  = sizeof(int),
+    .flags = M_OPT_TYPE_CHOICE,
     .parse = parse_choice,
     .print = print_choice,
     .copy  = copy_opt,
@@ -1087,6 +1088,7 @@ static int parse_float_aspect(struct mp_log *log, const m_option_t *opt,
 const m_option_type_t m_option_type_aspect = {
     .name  = "Aspect",
     .size  = sizeof(float),
+    .flags = M_OPT_TYPE_CHOICE,
     .parse = parse_float_aspect,
     .print = print_float,
     .pretty_print = print_float_f3,

options/m_option.h

@@ -443,6 +443,11 @@ char *format_file_size(int64_t size);
 // options can be used without "=" and value.
 #define M_OPT_TYPE_OPTIONAL_PARAM       (1 << 0)
 
+// Behaves fundamentally like a choice or a superset of it (all allowed string
+// values are from a fixed set, although other types of values like numbers
+// might be allowed too). E.g. m_option_type_choice and m_option_type_flag.
+#define M_OPT_TYPE_CHOICE               (1 << 1)
+
 ///////////////////////////// Parser flags /////////////////////////////////
 
 // OptionParserReturn