purge extension doesn't need "#!/usr/bin/env python".
(from the Debian package: deb_specific__hgpurge.py.patch)
Is there an error message when trying to diff non-existing files?
found: No such file or directory
not: No such file or directory
Is there an error message when trying to add non-existing files?
found: No such file or directory
not: No such file or directory