share-safe: enable by default (BC)
The feature have been around for a year (4 version) and is quite important.
Lets make it enabled by default.
Differential Revision: https://phab.mercurial-scm.org/D11997
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