doc/common.txt

bundlerepo: enforce reading from core repo only

We do not want anything computed with the bundle overlay to be written back in
the repo. Such write will likely contains invalid data.

The short terms goal of this change is to drop use of `_cacheabletip` in bundle
repo.

.. 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