config: update evolution-related config
Update the evolution helpers function to support both old-style configuration and
new-style configuration:
experimental.evolution=all is renamed into experimental.evolution=true
experimental.evolution=createmarkers is renamed into
experimental.evolution.createmarkers=true
experimental.evolution=allowunstable is renamed into
experimental.evolution.allowunstable=true
experimental.evolution=exchange is renamed into
experimental.evolution.exchange=true
We choose to not rename individual config options; keeping the same names
would easy the transition for users but it's something that could be easily
done in the future.
Differential Revision: https://phab.mercurial-scm.org/D1147
Greg Ward, author of the original bfiles extension
Na'Tosha Bard of Unity Technologies
Fog Creek Software
Special thanks to the University of Toronto and the UCOSP program