exchange: allow passing no includes/excludes to `pull()`
I would expect that `exchange.pull(includepats=[])` results in an empty list of
include patterns to be passed to the remote, but it doesn't currently because we
check for any truthy value instead of checking specifically for `not None`.
{
// Enforcing
"eqeqeq" : true, // true: Require triple equals (===) for comparison
"forin" : true, // true: Require filtering for..in loops with obj.hasOwnProperty()
"freeze" : true, // true: prohibits overwriting prototypes of native objects such as Array, Date etc.
"nonbsp" : true, // true: Prohibit "non-breaking whitespace" characters.
"undef" : true, // true: Require all non-global variables to be declared (prevents global leaks)
// Environments
"browser" : true // Web Browser (window, document, etc)
}