m_option: deprecate multiple items for -add etc.

This is more confusing than it helps, and forces escaping more stuff.
For example, for string lists we could remove all need for escaling with
-add and -pre.

The user can simply use multiple of those options.

DOCS/interface-changes.rst

@@ -50,6 +50,8 @@ Interface changes
         (the compatibility hacks for this will be removed after this release)
     - remove property `vo-performance`, and add `vo-passes` as a more general
       replacement
+    - deprecate passing multiple arguments to -add/-pre options (affects the
+      vf/af commands too)
  --- mpv 0.25.0 ---
     - remove opengl-cb dxva2 dummy hwdec interop
       (see git "vo_opengl: remove dxva2 dummy hwdec backend")

options/m_option.c

@@ -1159,8 +1159,6 @@ static int str_list_del(struct mp_log *log, char **del, int n, void *dst)
         talloc_free(lst[idx]);
         lst[idx] = NULL;
         s--;
-        if (i > 0)
-            mp_warn(log, "Passing multiple -del arguments is deprecated!\n");
     }
     talloc_free(del);
 
@@ -1282,6 +1280,11 @@ static int parse_str_list_impl(struct mp_log *log, const m_option_t *opt,
     res[n] = NULL;
     talloc_free(ptr);
 
+    if (op != OP_NONE && n > 1) {
+        mp_warn(log, "Passing multiple arguments to %.*s is deprecated!\n",
+                BSTR_P(name));
+    }
+
     switch (op) {
     case OP_ADD:
         return str_list_add(res, n, dst, 0);
@@ -2976,6 +2979,11 @@ static int parse_obj_settings_list(struct mp_log *log, const m_option_t *opt,
         }
     }
 
+    if (op != OP_NONE && res && res[0].name && res[1].name) {
+        mp_warn(log, "Passing more than 1 argument to %.*s is deprecated!\n",
+                BSTR_P(name));
+    }
+
     if (dst) {
         m_obj_settings_t *list = VAL(dst);
         if (op == OP_PRE) {