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" symlink || exit 80
hg init a
ln -s a link
cd a
echo foo > foo
hg status
hg status ../link