lua: add trusted metadata property

Add function `file_is_playlist` to parse the `trusted` property
of a file. This function will be used to upgrade the metadata
priority from `VLC_META_PRIORITY_BASIC` to `VLC_META_PRIORITY_PLAYLIST`
for files marked as trusted. Set the `trusted` property of CUE files
as they require playlist metadata priority.
Refs #4143

modules/lua/vlc.c

@@ -95,6 +95,18 @@ static int file_compare( const char **a, const char **b )
     return strcmp( *a, *b );
 }
 
+/* Function to parse the trusted property of a file */
+static bool file_is_playlist( lua_State *L )
+{
+    bool trusted = false;
+    lua_getfield(L, -1, "trusted");
+    if( !lua_isnil(L, -1) && lua_isboolean(L, -1) )
+        trusted = lua_toboolean(L, -1);
+
+    lua_pop( L, 1 );
+    return trusted;
+}
+
 static char **vlclua_dir_list_append( char **restrict list, char *basedir,
                                       const char *luadirname )
 {

share/lua/playlist/cue.lua

@@ -74,6 +74,7 @@ function cue_track( global, track )
     t.date = track.date or global.date
     t.description = global.comment
     t.tracknum = track.num
+    t.trusted = true
     t.options = { ":start-time=" .. track.index01}
 
     return t