options: remove weird --really-quiet special behavior

This was especially grating because it causes problems with the
option/property unification, uses as only thing OPT_FLAG_STORE, and
behaves weird with the client API or scripts.

It can be reimplemented in a much simpler way, although it needs
slightly more code. (Simpler because less special cases.)

DOCS/interface-changes.rst

@@ -36,6 +36,7 @@ Interface changes
     - renamed the TRCs `st2084` and `std-b67` to `pq` and `hlg` respectively
     - the "osd" command is deprecated (use "cycle osd-level")
     - --field-dominance is deprecated (no replacement)
+    - --really-quiet subtle behavior change
  --- mpv 0.25.0 ---
     - remove opengl-cb dxva2 dummy hwdec interop
       (see git "vo_opengl: remove dxva2 dummy hwdec backend")

common/msg.c

@@ -57,6 +57,7 @@ struct mp_log_root {
     int status_lines;   // number of current status lines
     bool color;
     int verbose;
+    bool really_quiet;
     bool force_stderr;
     struct mp_log_buffer **buffers;
     int num_buffers;
@@ -110,7 +111,9 @@ static void update_loglevel(struct mp_log *log)
 {
     struct mp_log_root *root = log->root;
     pthread_mutex_lock(&mp_msg_lock);
-    log->level = MSGL_STATUS + log->root->verbose; // default log level
+    log->level = MSGL_STATUS; // default log level
+    if (root->really_quiet)
+        log->level -= 10;
     for (int n = 0; root->msg_levels && root->msg_levels[n * 2 + 0]; n++) {
         if (match_mod(log->verbose_prefix, root->msg_levels[n * 2 + 0]))
             log->level = mp_msg_find_level(root->msg_levels[n * 2 + 1]);
@@ -511,6 +514,7 @@ void mp_msg_update_msglevels(struct mpv_global *global)
     pthread_mutex_lock(&mp_msg_lock);
 
     root->verbose = opts->verbose;
+    root->really_quiet = opts->msg_really_quiet;
     root->module = opts->msg_module;
     root->use_terminal = opts->use_terminal;
     root->show_time = opts->msg_time;

options/options.c

@@ -261,8 +261,7 @@ const m_option_t mp_opts[] = {
 
 // ------------------------- common options --------------------
     OPT_FLAG("quiet", quiet, 0),
-    OPT_FLAG_STORE("really-quiet", verbose,
-                   M_OPT_FIXED | CONF_PRE_PARSE | M_OPT_NOPROP, -10),
+    OPT_FLAG("really-quiet", msg_really_quiet, CONF_PRE_PARSE | UPDATE_TERM),
     OPT_FLAG("terminal", use_terminal, CONF_PRE_PARSE | UPDATE_TERM),
     OPT_GENERAL(char**, "msg-level", msg_levels, CONF_PRE_PARSE | UPDATE_TERM,
                 .type = &m_option_type_msglevels),

options/options.h

@@ -73,6 +73,7 @@ typedef struct MPOpts {
     int use_terminal;
     char *dump_stats;
     int verbose;
+    int msg_really_quiet;
     char **msg_levels;
     int msg_color;
     int msg_module;