tests/test-empty

use 'x is None' instead of 'x == None'

The built-in None object is a singleton and it is therefore safe to
compare memory addresses with is. It is also faster, how much depends
on the object being compared. For a simple type like str I get:

            | s = "foo" | s = None
  ----------+-----------+----------
  s == None | 0.25 usec | 0.21 usec
  s is None | 0.17 usec | 0.17 usec

#!/bin/sh

hg init a
cd a
hg log
hg grep wah
hg manifest
hg verify
ls .hg
ls .hg/store

cd ..
hg clone a b
cd b
hg verify
ls .hg
ls .hg/store