py3: workaround comparing NoneType and integers
Comparing None with integers was fine in Python 2 but returns error in Python 3
which is nice. This patch replaces None with -1 where sorting is done and some
related logic.
Differential Revision: https://phab.mercurial-scm.org/D3219
.. Common link and substitution definitions.
.. |hg(1)| replace:: **hg**\ (1)
.. _hg(1): hg.1.html
.. |hgrc(5)| replace:: **hgrc**\ (5)
.. _hgrc(5): hgrc.5.html
.. |hgignore(5)| replace:: **hgignore**\ (5)
.. _hgignore(5): hgignore.5.html