D616: context: add overlayworkingcontext and overlayworkingfilectx

[martinvonz (Martin von Zweigbergk)]

martinvonz added inline comments.

INLINE COMMENTS

> context.py:2009
> +            else:
> +                raise ProgrammingError("No such file or directory: %s" %
> +                                       self._path)

test-check-pyflakes.t fails with

  +  mercurial/context.py:2009: undefined name 'ProgrammingError'
  +  mercurial/context.py:2025: undefined name 'ProgrammingError'
  +  mercurial/context.py:2068: undefined name 'ProgrammingError'

I'll qualify it in flight

REPOSITORY
  rHG Mercurial

REVISION DETAIL
  https://phab.mercurial-scm.org/D616

To: phillco, #hg-reviewers
Cc: quark, martinvonz, mercurial-devel