qmplay2: detach sources acquisition to sources.nix

Because it uses fetchSubmodules, and maybe in the future it will
become discouraged.

pkgs/by-name/qm/qmplay2/package.nix

@@ -1,8 +1,8 @@
 {
   lib,
   alsa-lib,
+  callPackage,
   cmake,
-  fetchFromGitHub,
   ffmpeg,
   fribidi,
   game-music-emu,
@@ -23,17 +23,11 @@
   vulkan-tools,
 }:
 
+let
+  sources = callPackage ./sources.nix { };
+in
 stdenv.mkDerivation (finalAttrs: {
-  pname = "qmplay2";
-  version = "24.04.07";
-
-  src = fetchFromGitHub {
-    owner = "zaps166";
-    repo = "QMPlay2";
-    rev = finalAttrs.version;
-    fetchSubmodules = true;
-    hash = "sha256-WIDGApvl+aaB3Vdv0sHY+FHWqzreWWd3/xOLV11YfxM=";
-  };
+  inherit (sources.qmplay2) pname version src;
 
   nativeBuildInputs = [
     cmake

pkgs/by-name/qm/qmplay2/sources.nix

@@ -0,0 +1,21 @@
+{
+  fetchFromGitHub,
+}:
+
+{
+  qmplay2 = let
+    self = {
+      pname = "qmplay2";
+      version = "24.04.07";
+
+      src = fetchFromGitHub {
+        owner = "zaps166";
+        repo = "QMPlay2";
+        rev = self.version;
+        fetchSubmodules = true;
+        hash = "sha256-WIDGApvl+aaB3Vdv0sHY+FHWqzreWWd3/xOLV11YfxM=";
+      };
+    };
+  in
+    self;
+}