D2576: xdiff: add a python wrapper

[quark (Jun Wu)]

quark added a comment.


  Traditionally things under `mercurial.cext` has a pure equivalent. So it's cleaner to either make the changes directly in `mercurial.cext.bdiff`, or `mercurial/bdiff.c`. Or add a xdiff pure shim.

REPOSITORY
  rHG Mercurial

REVISION DETAIL
  https://phab.mercurial-scm.org/D2576

To: ryanmce, #hg-reviewers
Cc: quark, mercurial-devel