tests/test-revert-flags

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

"$TESTDIR/hghave" execbit || exit 80

hg init repo
cd repo
echo foo > foo
chmod 644 foo
hg ci -qAm '644'

chmod 755 foo
hg ci -qAm '755'

echo '% reverting to rev 0'
hg revert -a -r 0
hg st
hg diff --git