test-rebase-base: clarify it is about the "--base" flag
It happened several times that people use `test-rebase-base.t` as a general
purposed test file for rebase. But it is intended to be only related to the
`--base` flag. This patch split, renamed the test, and added a note to
clarify.
Differential Revision: https://phab.mercurial-scm.org/D975
FROM ubuntu:__CODENAME__
RUN apt-get update && apt-get install -y \
build-essential \
debhelper \
devscripts \
dh-python \
less \
python \
python-all-dev \
python-docutils \
unzip \
zip