tests/test-diff-binary-file

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
cp $TESTDIR/binfile.bin .
hg add binfile.bin
hg ci -m 'add binfile.bin'

echo >> binfile.bin
hg ci -m 'change binfile.bin'

hg revert -r 0 binfile.bin
hg ci -m 'revert binfile.bin'

echo % diff -r 0 -r 1
hg diff --nodates -r 0 -r 1

echo % diff -r 0 -r 2
hg diff --nodates -r 0 -r 2

echo % diff --git -r 0 -r 1
hg diff --git -r 0 -r 1

echo % diff --git -r 0 -r 2
hg diff --git -r 0 -r 2