command: prefix DVD title properties with "dvd-"

They're strictly DVD-only, so it's better to mark them as such. This
also documentes the "title" (now renamed to "dvd-title") property.

This also avoids collision with the --title option. (Technically, there
was no problem. But it might be confusing for users, since we have a
policy of naming properties and options the same if they refer to the
same underlying functionality.)

DOCS/man/en/input.rst

@@ -616,9 +616,12 @@ an option at runtime.
     Current MKV edition number. Setting this property to a different value will
     restart playback. The number of the first edition is 0.
 
-``titles``
+``dvd-titles``
     Number of DVD titles.
 
+``dvd-title``
+    Current DVD title number.
+
 ``chapters``
     Number of chapters.
 

player/command.c

@@ -436,9 +436,9 @@ static int mp_property_playtime_remaining(m_option_t *prop, int action,
     return property_time(prop, action, arg, remaining / speed);
 }
 
-/// Current title (RO)
-static int mp_property_title(m_option_t *prop, int action, void *arg,
-                             MPContext *mpctx)
+/// Current DVD title (RO)
+static int mp_property_dvd_title(m_option_t *prop, int action, void *arg,
+                                 MPContext *mpctx)
 {
     struct demuxer *demuxer = mpctx->master_demuxer;
     if (!demuxer || !demuxer->stream)
@@ -722,9 +722,9 @@ static int mp_property_quvi_format(m_option_t *prop, int action, void *arg,
     return mp_property_generic_option(prop, action, arg, mpctx);
 }
 
-/// Number of titles in file
-static int mp_property_titles(m_option_t *prop, int action, void *arg,
-                              MPContext *mpctx)
+/// Number of titles in DVD
+static int mp_property_dvd_titles(m_option_t *prop, int action, void *arg,
+                                  MPContext *mpctx)
 {
     struct demuxer *demuxer = mpctx->master_demuxer;
     unsigned int num_titles;
@@ -2118,12 +2118,12 @@ static const m_option_t mp_properties[] = {
       M_OPT_MIN, 0, 0, NULL },
     { "time-remaining", mp_property_remaining, CONF_TYPE_TIME },
     { "playtime-remaining", mp_property_playtime_remaining, CONF_TYPE_TIME },
-    { "title", mp_property_title, CONF_TYPE_INT, M_OPT_MIN, -1, 0, NULL },
+    { "dvd-title", mp_property_dvd_title, CONF_TYPE_INT, M_OPT_MIN, -1, 0, NULL },
     { "chapter", mp_property_chapter, CONF_TYPE_INT,
       M_OPT_MIN, -1, 0, NULL },
     M_OPTION_PROPERTY_CUSTOM("edition", mp_property_edition),
     M_OPTION_PROPERTY_CUSTOM("quvi-format", mp_property_quvi_format),
-    { "titles", mp_property_titles, CONF_TYPE_INT,
+    { "dvd-titles", mp_property_dvd_titles, CONF_TYPE_INT,
       0, 0, 0, NULL },
     { "chapters", mp_property_chapters, CONF_TYPE_INT,
       0, 0, 0, NULL },