TOOLS/lua/autoload: may specify loading only one type of files

Under the current file loading logic, a video file and an external
audio track next to it will both be added to the playlist, which
most users don't wish to happen. Having an option that tells the
script to load only one type of files (video, audio, or image)
can avoid this problem. It may also come in handy for people who
have different types of files mixed in a folder but wish to consume
only one type of media at a time.

TOOLS/lua/autoload.lua

@@ -20,6 +20,7 @@ additional_image_exts=list,of,ext
 additional_video_exts=list,of,ext
 additional_audio_exts=list,of,ext
 ignore_hidden=yes
+same_type=yes
 
 --]]
 
@@ -37,7 +38,8 @@ o = {
     additional_image_exts = "",
     additional_video_exts = "",
     additional_audio_exts = "",
-    ignore_hidden = true
+    ignore_hidden = true,
+    same_type = false
 }
 options.read_options(o)
 
@@ -153,15 +155,28 @@ function find_and_add_entries()
     end
 
     pl_count = mp.get_property_number("playlist-count", 1)
+    this_ext = get_extension(filename)
     -- check if this is a manually made playlist
     if (pl_count > 1 and autoloaded == nil) or
-       (pl_count == 1 and EXTENSIONS[string.lower(get_extension(filename))] == nil) then
+       (pl_count == 1 and EXTENSIONS[string.lower(this_ext)] == nil) then
         msg.verbose("stopping: manually made playlist")
         return
     else
         autoloaded = true
     end
 
+    if o.same_type then
+        if EXTENSIONS_VIDEO[string.lower(this_ext)] ~= nil then
+            EXTENSIONS_TARGET = EXTENSIONS_VIDEO
+        elseif EXTENSIONS_AUDIO[string.lower(this_ext)] ~= nil then
+            EXTENSIONS_TARGET = EXTENSIONS_AUDIO
+        else
+            EXTENSIONS_TARGET = EXTENSIONS_IMAGES
+        end
+    else
+        EXTENSIONS_TARGET = EXTENSIONS
+    end
+
     local pl = mp.get_property_native("playlist", {})
     local pl_current = mp.get_property_number("playlist-pos-1", 1)
     msg.trace(("playlist-pos-1: %s, playlist: %s"):format(pl_current,
@@ -182,7 +197,7 @@ function find_and_add_entries()
         if ext == nil then
             return false
         end
-        return EXTENSIONS[string.lower(ext)]
+        return EXTENSIONS_TARGET[string.lower(ext)]
     end)
     alphanumsort(files)