contrib/docker/debian-jessie

contrib/perf: fix perfmergecalculate

merge.calculateupdates requires an array of ancestors and followcopies

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