As I wrote in the last blog post, the static site generator that I use to publish this post is Pelican. Rather than generating the HTML on my machine and then pushing it to the gh-pages branch of github.com/thomastweets/blog.thomasemmerling.de I automatized this process using Travis CI. Travis CI is a continuous integration that is free to use for open source projects. It can not only run automated tests of your project but also trigger deployment tasks when the build is successful.

Using information from two blogs I was able to let Travis CI react on any push to GitHub and automatically generate HTML from the Pelican sources and push them back to the gh-pages branch. Here is how to do that:

• If you have not done that yet: Create a repository on GitHub called (e.g.) blog.thomasemmerling.de.
• Add it as a remote to your local git repository from command line (if you use ssh-keys for authentication - you should do so! how to generate and use them):

# Go to your local Pelican sources
cd ~/blog
# Add the remote GitHub repository
git remote add origin git@github.com:thomastweets/blog.thomasemmerling.de.git
# set the default upstream and push to it
git push --set-upstream origin master

• As Travis CI needs to be able to push to your GitHub repository you need to authenticate it. As you do not want to store any passwords, ssh, or API keys in your repo or the Travis CI configuration the easiest way is to use the travis command line tool that is available as a gem to encrypt an Authentication Token for GitHub so that Travis CI can decrypt it when needed. First we need to install it:

# on OSX using the default Ruby installation
sudo gem install travis

• Now we create a personal access token on GitHub to use with Travis CI. Follow these instructions to do so. I named mine TravisCI blog.thomasemmerling.de and kept the standard scope settings. Copy the token when you created it as you will not be able to see it again after you close the page.
• Encrypt the token with the travis command line tool:

# where 'your_token' is the token from the last step
travis encrypt GH_TOKEN=your_token

• Create a file .travis.yml (mind the dot at the beginning!) in the root of your git repository and paste the following (replace the encrypted part after - secure: with what travis encrypt got back to you):

language: python
branches:
  only:
  - master
install:
- pip install pelican
- pip install ghp-import
- pip install markdown
script:
- make publish
- make github
env:
  global:
  - secure: "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"

• In the Makefile in the root directory add (or change) the github subcommand (this makes the make github command in the .travis.yml file work):

github: publish
    ghp-import -n $(OUTPUTDIR)
    @git push -fq https://${GH_TOKEN}@github.com/$(TRAVIS_REPO_SLUG).git gh-pages > /dev/null

• Add the .travis.yml file and the Makefile to your git repository, commit, and push to GitHub.

Now, if all went well, after some minutes you should see a successful build in Travis CI and the new version of your homepage/blog at the .github.io address (or in my case the custom domain).