Incrementally improve your Drupal code

.travis.yml

language: php
sudo: false

php:
  - 5.6

install:
  # Remove xdebug to make composer faster.
  - phpenv config-rm xdebug.ini

  # add composer's global bin directory to the path
  - export PATH="$HOME/.composer/vendor/bin:$PATH"

  # Install PHP_CodeSniffer and Drupal config
  - composer global require drupal/coder
  - phpcs --config-set installed_paths ~/.composer/vendor/drupal/coder/coder_sniffer

before_script:
  # This slows things down but it ensures all remote branches are fetched.
  - git config remote.origin.fetch "+refs/heads/*:refs/remotes/origin/*"
  - git fetch --unshallow
  - git fetch origin

script:
  # Check code sniffer compliance.
  - git diff --name-only origin/master | xargs phpcs --standard=Drupal

# Optional slack notifications.
notifications:
  slack:
    rooms:
      - subdomain:token#channel

git diff --name-only origin/master includes paths to files that have been deleted

git diff --name-only origin/master --diff-filter=ACMRTUXB | xargs phpcs --standard=Drupal will filter deleted files.