D210: pushvars: move fb extension pushvars to core

[durin42 (Augie Fackler)]

durin42 accepted this revision.
durin42 added a comment.
This revision is now accepted and ready to land.


  I like this, it opens the doors to some things I've wanted to do for a while.

REPOSITORY
  rHG Mercurial

REVISION DETAIL
  https://phab.mercurial-scm.org/D210

To: pulkit, #hg-reviewers, durin42
Cc: quark, durin42, akushner, mercurial-devel