Travis

Recommended free CI service.

Their docs are helpful and cover most use cases and problems.

Configuration

The CI process is prepared with the help of a YAML file, the .travis.yml. All projects include one of these.

As commented before, all the information is included in their docs.

Environmental variables

Remember that Travis gives support to environmental variables, which can be configured for each project. This is preffered to using encrypred variables in the YAML file.

Integration

Travis integrates well with other services such as Github or Bintray.

Complex flows

By default Travis only gives support to simple CI flows. It is recommended using shell scripts to cover this limitation.

There is a set of CI scripts which can help with this.