Fix mkdcd

home/fish.nix

@@ -35,6 +35,10 @@
     mkdcd = {
       argumentNames = [ "target" ];
       body = ''
+        if test -z "$target"
+          echo "mkdcd requires an argument" 1>&2
+          return 1
+        end
         mkdir -p $target
         cd $target
       '';