extensions: add wrappedfunction() context manager Several extensions exist that temporarily want to wrap a function (at least narrowhg, any many of the extensions in hg-experimental). That's why we have the unwrapfunction() that was introduced in 19578bb84731 (extensions: add unwrapfunction to undo wrapfunction, 2016-08-10). This patch adds a simple wrappedfunction() that returns a context manager. Differential Revision: https://phab.mercurial-scm.org/D472

FROM debian:__CODENAME__
RUN apt-get update && apt-get install -y \
  build-essential \
  debhelper \
  dh-python \
  devscripts \
  less \
  python \
  python-all-dev \
  python-docutils \
  zip \
  unzip