doc/common.txt

import: don't strip '#' lines from patch descriptions (issue 2417)

Previously no '# ' lines came through the parser.

Now only the first '# ' lines are processed, from '# HG changeset patch' and to
the first line not starting with '# '.

.. 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