mpv: fix issue #1725 and add tests (#1726)

Closes issue #1725.

This allows mpv module to be customized with support for more advanced
features than the `programs.mpv.scripts` current support. For example,
with this change now this is possible:

```nix
{
  programs.mpv.package = (pkgs.wrapMpv (pkgs.mpv-unwrapped.override {
    vapoursynthSupport = true;
  }) {
    extraMakeWrapperArgs = [
      "--prefix" "LD_LIBRARY_PATH" ":" "${pkgs.vapoursynth-mvtools}/lib/vapoursynth"
    ];
  });
}

```

Since `programs.mpv.package` doesn't necessary reflect the final
derivation anymore (see #1524), we introduce `programs.mpv.finalPackage`
that has the resulting derivation.

This includes 2 tests:
- One to check if everything is alright with mpv
- Other to validate our assertion that package and scripts can't be
  passed both at the same time

* docs: document recent mpv module changes

* mpv: add thiagokokada as maintainer

tests/modules/programs/mpv/default.nix

@@ -0,0 +1,4 @@
+{
+  mpv-example-settings = ./mpv-example-settings.nix;
+  mpv-invalid-settings = ./mpv-invalid-settings.nix;
+}

tests/modules/programs/mpv/mpv-example-settings-expected-bindings

@@ -0,0 +1,3 @@
+Alt+0 set window-scale 0.5
+WHEEL_DOWN seek -10
+WHEEL_UP seek 10

tests/modules/programs/mpv/mpv-example-settings-expected-config

@@ -0,0 +1,13 @@
+profile=%6%gpu-hq
+
+cache-default=%7%4000000
+force-window=%3%yes
+ytdl-format=%19%bestvideo+bestaudio
+
+[fast]
+vo=%5%vdpau
+
+[protocol.dvd]
+alang=%2%en
+profile-desc=%26%profile for dvd:// streams
+

tests/modules/programs/mpv/mpv-example-settings.nix

@@ -0,0 +1,46 @@
+{ config, lib, pkgs, ... }:
+
+{
+  config = {
+    programs.mpv = {
+      enable = true;
+      package = pkgs.mpvDummy;
+
+      bindings = {
+        WHEEL_UP = "seek 10";
+        WHEEL_DOWN = "seek -10";
+        "Alt+0" = "set window-scale 0.5";
+      };
+
+      config = {
+        force-window = true;
+        ytdl-format = "bestvideo+bestaudio";
+        cache-default = 4000000;
+      };
+
+      profiles = {
+        fast = { vo = "vdpau"; };
+        "protocol.dvd" = {
+          profile-desc = "profile for dvd:// streams";
+          alang = "en";
+        };
+      };
+
+      defaultProfiles = [ "gpu-hq" ];
+    };
+
+    nixpkgs.overlays = [
+      (self: super: { mpvDummy = pkgs.runCommandLocal "mpv" { } "mkdir $out"; })
+    ];
+
+    nmt.script = ''
+      assertFileContent \
+         home-files/.config/mpv/mpv.conf \
+         ${./mpv-example-settings-expected-config}
+      assertFileContent \
+         home-files/.config/mpv/input.conf \
+         ${./mpv-example-settings-expected-bindings}
+    '';
+  };
+
+}

tests/modules/programs/mpv/mpv-invalid-settings-expected.json

@@ -0,0 +1 @@
+["The programs.mpv \"package\" option is mutually exclusive with \"scripts\" option."]

tests/modules/programs/mpv/mpv-invalid-settings.nix

@@ -0,0 +1,29 @@
+{ config, lib, pkgs, ... }:
+
+{
+  config = {
+    programs.mpv = {
+      enable = true;
+      package = pkgs.mpvDummy;
+      scripts = [ pkgs.mpvScript ];
+    };
+
+    nixpkgs.overlays = [
+      (self: super: {
+        mpvDummy = pkgs.runCommandLocal "mpv" { } "mkdir $out";
+        mpvScript =
+          pkgs.runCommandLocal "mpvScript" { scriptName = "something"; }
+          "mkdir $out";
+      })
+    ];
+
+    home.file.result.text = builtins.toJSON
+      (map (a: a.message) (lib.filter (a: !a.assertion) config.assertions));
+
+    nmt.script = ''
+      assertFileContent \
+         home-files/result \
+         ${./mpv-invalid-settings-expected.json}
+    '';
+  };
+}