Why switch from building Docker images in each Travis-CI build to pulling form the Docker Hub?
The docker build step can often times be the slowest step in a build process. In this example case (Aptly_cli), approximately 6 minutes can be shaved off.
Gain full control over Docker image being used for testing by leveraging a central storage platform such as Docker Hub
In this case I use a Rakefile to managed the Docker commands. A simple update to Rakefile with the 'pull' command needed will do the trick.
Here is it in action, making an update to the Dockerfile and pushing to the Docker Hub for later use by Travis-CI.
Then apply the changed build step in the .travis-ci.yml
POOF! Rocking out some faster build times now.