show git commit in about dialog

linux/nix/default.nix

@@ -20,6 +20,7 @@
         let
           default = pkgs.callPackage ./pkg {
             src = self;
+            commit = self.shortRev or self.dirtyShortRev;
           };
         in
         {

linux/nix/pkg/default.nix

@@ -6,6 +6,7 @@
   libclang,
   flutter,
   src,
+  commit ? "dev",
 }:
 
 flutter.buildFlutterApplication {
@@ -19,6 +20,10 @@ flutter.buildFlutterApplication {
     packageRun build_runner build
   '';
 
+  flutterBuildFlags = [
+    "--dart-define=GIT_COMMIT=${commit}"
+  ];
+
   buildInputs = [
     mpv-unwrapped
     libass