patch: stop changing current directory before patching
_applydiff() patcher argument was added to help hgsubversion like extension
monkeypatching the patching process. While it could be removed at this point, I
prefer to leave it until patch.py is completely refactored and there is a valid
and tested alternative.
.. 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