Run travis-ci locally using R-base docker image

local-travis-ci.sh

# adapted from: https://stackoverflow.com/a/41935867/171659
# choose the image according to the language chosen in .travis.yml
mkdir -p "$PWD":/home/docker
docker run -ti --rm -v "$PWD":/home/docker -w /home/docker -u docker r-base /bin/bash

# now that you are in the docker image, switch to the travis user
sudo - travis

apt-get install ruby

# Install travis-build to generate a .sh out of .travis.yml
mkdir builds
cd builds
git clone https://github.com/travis-ci/travis-build.git
cd travis-build
gem install travis
# to create ~/.travis
travis version
ln -s `pwd` ~/.travis/travis-build
bundle install

# Create project dir, assuming your project is `AUTHOR/PROJECT` on GitHub
cd ~/builds
mkdir AUTHOR
cd AUTHOR
git clone https://github.com/AUTHOR/PROJECT.git
cd PROJECT
# change to the branch or commit you want to investigate
travis compile > ci.sh
# You most likely will need to edit ci.sh as it ignores matrix and env
bash ci.sh