mercurial/helptext/common.txt

dirstate: only reload the dirstate when it may have changed

This reinstall the equivalent of what the `filecache` was doing. However it does
it at the dirstate level.

There is a double motivation for this:
- This avoid duplicating logic with the dirstate "identity" logic.
- This increase the lifetime of the `dirstate` object, helping to implement
  change scoping.

.. 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