chistedit: add option to show order of commits in opposite order
Many users (including me) expect the order of commits in histedit to
match the order in hg log -G and are confused because it
doesnn't. This patch adds an option to show later commits first in the
list. I've only added support for it in chistedit for now. As a
consequence, I've marked the config option experimental (I think it
should apply to both interfaces before it graduates).
Differential Revision: https://phab.mercurial-scm.org/D11669