add comments in cachefunc

mercurial/util.py

@@ -26,8 +26,11 b' class SignalInterrupt(Exception):'
 
 def cachefunc(func):
     '''cache the result of function calls'''
+    # XXX doesn't handle keywords args
     cache = {}
     if func.func_code.co_argcount == 1:
+        # we gain a small amount of time because
+        # we don't need to pack/unpack the list
         def f(arg):
             if arg not in cache:
                 cache[arg] = func(arg)