tests(travis): Optimize Travis build steps for faster CI runs

dist: trusty

dist: xenial

language: php

sudo: false

# Cache composer downloads to speed up the composer install step.

cache:

  directories:

    - $HOME/.composer/cache

matrix:

  fast_finish: true

  include:

    - php: 7.0

    - php: 7.1

    - php: 7.2

    - php: nightly

    - php: hhvm

  allow_failures:

    - php: hhvm

    - php: nightly

    - php: 7.3

before_install:

  # Speed up build time by disabling Xdebug when its not needed.

  - phpenv config-rm xdebug.ini || echo 'No xdebug config.'

  # Circumvent a bug in the travis HHVM image - ships with incompatible PHPUnit.

  - if [[ $TRAVIS_PHP_VERSION == hhv* ]]; then composer self-update; fi

  - if [[ $TRAVIS_PHP_VERSION == hhv* ]]; then composer require phpunit/phpunit:~4.0; fi

  - if [[ $TRAVIS_PHP_VERSION == hhv* ]]; then composer install; fi

before_script:

  # We don't have a composer.lock file because we always want to test with