doc/common.txt

addremove: don't audit the path for paths already in the dirstate

Now that dirstate.walk returns None for paths under symlink directories,
addremove doesn't need to validate each path it sees to look for files
under symlinks.

On a large repository this brings addremove from 6.3 seconds down to 3.65 (42%)
since addremove no longer has to stat every directory of every file to determine
if the file is inside a symlink directory. I put it through our benchmark and
see no perf hit to any other commands.

.. 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