trydiff: move git-header code out of diffline function
This collects more of the code for writing git headers in a single
place and makes diffline() close on a few variables less.
FROM centos:centos7
RUN yum install -y gcc
RUN yum install -y python-devel python-docutils
RUN yum install -y make
RUN yum install -y rpm-build
RUN yum install -y gettext
RUN yum install -y tar
# For creating repo meta data
RUN yum install -y createrepo