CI: switch to GitHub Actions - step 3: quick test stage

This commit:
* Adds a GH Actions workflow for the CI checks which were previously run on Travis in the `quicktest` stage.
* Removes that part of the `.travis.yml` configuration.

Notes:
1. Previously, this "stage" would run on all `push` events, except when merging to `master` or `develop`.
    The current set-up still does so, with one exception: pushes to `develop` will now use this quicktest instead of the full test.
    `develop` is a protected branch anyhow, so all merges will already have had the full test run in the pull request.
    For merges to `master`, the full Test run will still be used as that will generally mean we're getting ready to tag a release and some extra safety checking before a release is not a bad thing.
2. This also updates the "high" PHP version for the "quicktest" against PHPCS `dev-master` from PHP 7.4 to PHP 8.0 by using `latest` which translates to "latest stable PHP release".

.github/workflows/quicktest.yml

@@ -0,0 +1,69 @@
+name: Quicktest
+
+on:
+  # Run on pushes, including merges, to all branches except `master`.
+  push:
+    branches-ignore:
+      - master
+    paths-ignore:
+      - '**.md'
+      - 'docs/**'
+
+jobs:
+  #### QUICK TEST STAGE ####
+  # This is a much quicker test which only runs the unit tests and linting against the low/high
+  # supported PHP/PHPCS combinations.
+  # These are basically the same builds as in the Test->Coverage workflow, but then without doing
+  # the code-coverage.
+  quicktest:
+    runs-on: ubuntu-latest
+
+    strategy:
+      matrix:
+        php: ['5.4', 'latest']
+        phpcs_version: ['dev-master']
+
+        include:
+          - php: '7.3'
+            phpcs_version: '2.9.2'
+          - php: '5.4'
+            phpcs_version: '2.6.0'
+
+    name: "QTest${{ matrix.phpcs_version == 'dev-master' && ' + Lint' || '' }}: PHP ${{ matrix.php }} - PHPCS ${{ matrix.phpcs_version }}"
+
+    steps:
+      - name: Checkout code
+        uses: actions/checkout@v2
+
+      # On stable PHPCS versions, allow for PHP deprecation notices.
+      # Unit tests don't need to fail on those for stable releases where those issues won't get fixed anymore.
+      - name: Setup ini config
+        id: set_ini
+        run: |
+          if [ "${{ matrix.phpcs_version }}" != "dev-master" ]; then
+            echo '::set-output name=PHP_INI::error_reporting=E_ALL & ~E_DEPRECATED'
+          else
+            echo '::set-output name=PHP_INI::error_reporting=E_ALL'
+          fi
+
+      - name: Install PHP
+        uses: shivammathur/setup-php@v2
+        with:
+          php-version: ${{ matrix.php }}
+          ini-values: ${{ steps.set_ini.outputs.PHP_INI }}
+          coverage: none
+
+      - name: 'Composer: set PHPCS version for tests'
+        run: composer require --no-update squizlabs/php_codesniffer:"${{ matrix.phpcs_version }}"
+
+      # Install dependencies and handle caching in one go.
+      # @link https://github.com/marketplace/actions/install-composer-dependencies
+      - name: Install Composer dependencies
+        uses: "ramsey/composer-install@v1"
+
+      - name: Lint against parse errors
+        if: matrix.phpcs_version == 'dev-master'
+        run: composer lint
+
+      - name: Run the unit tests
+        run: vendor/bin/phpunit --no-coverage

.travis.yml

@@ -31,8 +31,6 @@ env:
 # Note: for pull requests, "develop" is the base branch name.
 # See: https://docs.travis-ci.com/user/conditions-v1
 stages:
-  - name: quicktest
-    if: type = push AND branch NOT IN (master, develop)
   - name: test
     if: branch IN (master, develop)
   - name: coverage
@@ -41,28 +39,6 @@ stages:
 jobs:
   fast_finish: true
   include:
-    #### QUICK TEST STAGE ####
-    # This is a much quicker test which only runs the unit tests and linting against the low/high
-    # supported PHP/PHPCS combinations.
-    # These are basically the same builds as in the Coverage stage, but then without doing
-    # the code-coverage.
-    - stage: quicktest
-      php: 7.4
-      env: PHPCS_VERSION="dev-master" LINT=1
-    - stage: quicktest
-      php: 7.3
-      # PHPCS is only compatible with PHP 7.3 as of version 3.3.1/2.9.2.
-      env: PHPCS_VERSION="2.9.2"
-
-    - stage: quicktest
-      php: 5.4
-      dist: trusty
-      env: PHPCS_VERSION="dev-master" LINT=1
-    - stage: quicktest
-      php: 5.4
-      dist: trusty
-      env: PHPCS_VERSION="2.6.0"
-
     #### TEST STAGE ####
     # Additional builds to prevent issues with PHPCS versions incompatible with certain PHP versions.
     - stage: test