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