cmdutil: make options argument optional

There is not reason to force passing of an empty options list.

mercurial/cmdutil.py

@@ -2014,12 +2014,12 b' def command(table):'
     '''returns a function object bound to table which can be used as
     a decorator for populating table as a command table'''
 
-    def cmd(name, options, synopsis=None):
+    def cmd(name, options=(), synopsis=None):
         def decorator(func):
             if synopsis:
-                table[name] = func, options[:], synopsis
+                table[name] = func, list(options), synopsis
             else:
-                table[name] = func, options[:]
+                table[name] = func, list(options)
             return func
         return decorator