Continuous Deployment with Github Pages

2013-12-12 2 minute read #ci/cd

Or how to let Travis-CI merge into master if the build is successful.

It is way easier than I thought.

Prerequisites

The travis gem
Travis-CI integration up and running (ie .travis.yml is set up).

Step 1: Acquire Github Access Token

This is required because we don't want to write our Github username and password anywhere. Go to your Github Application Settings and create a new Token.

Step 2: Encrypt the token

Even the Token is not something to post on your Twitter.

travis encrypt -a - GITHUB_TOKEN=your_generated_token

Your token will be encrypted and automatically added to your .travis.yml file.

Step 3: Add some magic to your Travis config

'nuff said. Add these lines to .travis.yml (note this are only two lines):

after_success:
- '[ "${TRAVIS_BRANCH}" = "stable" ] && git push https://${GITHUB_TOKEN}:[email protected]/${TRAVIS_REPO_SLUG}.git HEAD:master'

Now for some explanation: The first part, [ "${TRAVIS_BRANCH}" = "stable" ] && only runs the following command if the current branch name is "stable". You can omit this if you want to merge from ANY branch, or change it to use another branch.

The second part, git push https://${GITHUB_TOKEN}:[email protected]/${TRAVIS_REPO_SLUG}.git HEAD:master' actually pushes the currently checked out state into master.

$GITHUB_TOKEN holds our Token from above
$TRAVIS_REPO_SLUG holds github_username/github_repo_name (in my case this is mhutter/mhutte.github.io).

Back story

To ensure new pages don't break Jekyll (as I managed earlier this month), I use Travis-CI.

I started working on a development branch and only merging into master after the Travis build succeeded. However, being the lazy guy I am I asked myself: "Wouldn't it be nice to let Travis automatically merge into master if the build succeeds?"