match: introduce nevermatcher for when no ignore files are present
952017471f93 introduced a deterministic `__repr__` for ignores. However, it
didn't account for when ignore was `util.never`. This broke fsmonitor's ignore
change detection -- with an empty hgignore, it would kick in all the time.
Introduce `nevermatcher` and switch to it. This neatly parallels
`alwaysmatcher`.
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