functions/cd: Optimize check for too many args

This ran two `test`s a `count` and one `echo`, which is a bit wasteful.

So instead, for the common case where you pass one argument, this will
run one `set -q`.

This can save off ~160 microseconds for each ordinary `cd`, which
speeds it up by a factor of ~2 (so 1000 runs of cd might take 260ms
instead of 550ms).

Ideally the cd function would just be incorporated into the builtin,
but that's a bigger change.

share/functions/cd.fish

@@ -4,7 +4,10 @@
 function cd --description "Change directory"
     set -l MAX_DIR_HIST 25
 
-    if test (count $argv) -gt (test "$argv[1]" = "--" && echo 2 || echo 1)
+    if set -q argv[2]; and begin
+            set -q argv[3]
+            or not test "$argv[1]" = --
+        end
         printf "%s\n" (_ "Too many args for cd command") >&2
         return 1
     end