[nix] Add a shell function for updating Nix

nix/hosts/alymac/zsh.nix

@@ -13,6 +13,14 @@
       export PATH="$PATH:$HOME/.npm-packages/bin"
       export FRENYARD_SCALE=2.40
       export RETHINK_API="https://rethink.alyxia.dev"
+
+      function violent-update() {
+        # <https://github.com/adryd325/dotfiles/blob/c52d10f0cb4b54ee46e2ac5b01b8be9f8d57973d/install.sh#L17>
+        sudo -v; while true; do sudo -n true; sleep 60; kill -0 "$$" || exit; done 2>/dev/null &
+        cd "$HOME/.dotfiles/nix";
+        sudo nix-channel --update && nix-channel --update;
+        sudo nix-env -u;
+      }
     '';
   };
 }