mpv: Use youtube-dl’s default format

mpv overrides my custom format with `bestvideo+bestaudio/best`
(youtube-dl upstream default). This applies a patch (from upstream) that
adds a magic value to remove the override. Since home-manager’s mpv
module only supports overriding the mpv package in 21.05, it is done in
the overlay.

Fixes #39.

pkgs/default.nix

@@ -17,4 +17,15 @@ in
   };
 
   aria2_exporter = import srcs.aria2_exporter { pkgs = self; };
+
+  # FIXME: 21.05: Move to home-manager module package attribute
+  mpv-unwrapped = super.mpv-unwrapped.overrideAttrs (o: o // {
+    patches = [
+      # FIXME: 21.05: Remove since it has mpv 0.33
+      (super.fetchpatch {
+        url = "https://github.com/mpv-player/mpv/commit/43c13e5ea23230edca38426d4a9eed049a70890e.patch";
+        sha256 = "0g73ws36cs2hfzqck6xiaimj5yd5hz68b4wf3qayyv4nrf5sz02c";
+      })
+    ];
+  });
 }

users/simon/modules/mpv.nix

@@ -103,6 +103,9 @@ in
 
       # Lossless screenshots
       screenshot-format = "png";
+
+      # Use youtube-dl’s format configuration
+      ytdl-format = "ytdl";
     };
 
     bindings = {