mg.meta.mainProgram: init

pkgs/applications/editors/mg/default.nix

···
     description = "Micro GNU/emacs, a portable version of the mg maintained by the OpenBSD team";
     homepage = "https://man.openbsd.org/OpenBSD-current/man1/mg.1";
     license = licenses.publicDomain;
+    mainProgram = "mg";
     platforms = platforms.all;
   };
 }