narrow: move changegroup.supportedoutgoingversions() override to core
Also document why we need cg3 or higher.
Differential Revision: https://phab.mercurial-scm.org/D2488
FROM fedora:21
RUN yum install -y \
gcc \
gettext \
make \
python-devel \
python-docutils \
rpm-build
# For creating repo meta data
RUN yum install -y createrepo