upgrade: use progress helper
A minor side-effect is that we no longer print the progress at 0 (and
that we don't re-print it at its current value when starting the next
manifest/file).
Differential Revision: https://phab.mercurial-scm.org/D3800
.. 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