GH Actions: "pin" all action runners

Recently there has been more and more focus on securing GH Actions workflows - in part due to some incidents.

The problem with "unpinned" action runners is as follows:
* Tags are mutable, which means that a tag could point to a safe commit today, but to a malicious commit tomorrow.
    Note that GitHub is currently beta-testing a new "immutable releases" feature (= tags and release artifacts can not be changed anymore once the release is published), but whether that has much effect depends on the ecosystem of the packages using the feature.
    Aside from that, it will likely take years before all projects adopt _immutable releases_.
* Action runners often don't even point to a tag, but to a branch, making the used action runner a moving target.
    _Note: this type of "floating major" for action runners used to be promoted as good practice when the ecosystem was "young". Insights have since changed._

While it is convenient to use "floating majors" of action runners, as this means you only need to update the workflows on a new major release of the action runner, the price is higher risk of malicious code being executed in workflows.

Dependabot, by now, can automatically submit PRs to update pinned action runners too, as long as the commit-hash pinned runner is followed by a comment listing the released version the commit is pointing to.

So, what with Dependabot being capable of updating workflows with pinned action runners, I believe it is time to update the workflows to the _current_ best practice of using commit-hash pinned action runners.

The downside of this change is that there will be more frequent Dependabot PRs.

If this would become a burden/irritating, the following mitigations can be implemented:
1. Updating the Dependabot config to group updates instead of sending individual PRs per action runner.
2. A workflow to automatically merge Dependabot PRs as long as CI passes.

Ref: https://docs.github.com/en/actions/reference/security/secure-use#using-third-party-actions

Author: jrfnl

.github/workflows/cs.yml

@@ -21,10 +21,10 @@ jobs:
 
     steps:
       - name: Checkout code
-        uses: actions/checkout@v5
+        uses: actions/checkout@08c6903cd8c0fde910a37f88322edcfb5dd907a8 # v5.0.0
 
       - name: Install PHP
-        uses: shivammathur/setup-php@v2
+        uses: shivammathur/setup-php@ec406be512d7077f68eed36e63f4d91bc006edc4 # master
         with:
           php-version: 'latest'
           coverage: none
@@ -46,56 +46,56 @@ jobs:
       # Install dependencies and handle caching in one go.
       # @link https://github.com/marketplace/actions/install-php-dependencies-with-composer
       - name: Install Composer dependencies
-        uses: "ramsey/composer-install@v3"
+        uses: "ramsey/composer-install@3cf229dc2919194e9e36783941438d17239e8520" # 3.1.1
         with:
           # Bust the cache at least once a month - output format: YYYY-MM.
           custom-cache-suffix: $(date -u "+%Y-%m")
 
       # Validate the XSD and XML files against schema.
       - name: Validate Docs XSD against schema
-        uses: phpcsstandards/xmllint-validate@v1
+        uses: phpcsstandards/xmllint-validate@0fd9c4a9046055f621fca4bbdccb8eab1fd59fdc # v1.0.1
         with:
           pattern: "DocsXsd/phpcsdocs.xsd"
           xsd-url: "https://www.w3.org/2012/04/XMLSchema.xsd"
 
       - name: Validate PHPCSDebug ruleset against schema
-        uses: phpcsstandards/xmllint-validate@v1
+        uses: phpcsstandards/xmllint-validate@0fd9c4a9046055f621fca4bbdccb8eab1fd59fdc # v1.0.1
         with:
           pattern: "PHPCSDebug/ruleset.xml"
           xsd-file: "vendor/squizlabs/php_codesniffer/phpcs.xsd"
 
       - name: Validate docs against schema
-        uses: phpcsstandards/xmllint-validate@v1
+        uses: phpcsstandards/xmllint-validate@0fd9c4a9046055f621fca4bbdccb8eab1fd59fdc # v1.0.1
         with:
           pattern: "PHPCSDebug/Docs/*/*Standard.xml"
           xsd-file: "DocsXsd/phpcsdocs.xsd"
 
       - name: Validate Project PHPCS ruleset against schema
-        uses: phpcsstandards/xmllint-validate@v1
+        uses: phpcsstandards/xmllint-validate@0fd9c4a9046055f621fca4bbdccb8eab1fd59fdc # v1.0.1
         with:
           pattern: "phpcs.xml.dist"
           xsd-file: "vendor/squizlabs/php_codesniffer/phpcs.xsd"
 
       - name: "Validate PHPUnit < 10 config for use with PHPUnit 8"
-        uses: phpcsstandards/xmllint-validate@v1
+        uses: phpcsstandards/xmllint-validate@0fd9c4a9046055f621fca4bbdccb8eab1fd59fdc # v1.0.1
         with:
           pattern: "phpunitlte9.xml.dist"
           xsd-file: "vendor/phpunit/phpunit/schema/8.5.xsd"
 
       - name: "Validate PHPUnit < 10 config for use with PHPUnit 9"
-        uses: phpcsstandards/xmllint-validate@v1
+        uses: phpcsstandards/xmllint-validate@0fd9c4a9046055f621fca4bbdccb8eab1fd59fdc # v1.0.1
         with:
           pattern: "phpunitlte9.xml.dist"
           xsd-file: "vendor/phpunit/phpunit/schema/9.5.xsd"
 
       - name: "Validate PHPUnit 10+ config for use with PHPUnit 10"
-        uses: phpcsstandards/xmllint-validate@v1
+        uses: phpcsstandards/xmllint-validate@0fd9c4a9046055f621fca4bbdccb8eab1fd59fdc # v1.0.1
         with:
           pattern: "phpunit.xml.dist"
           xsd-file: "vendor/phpunit/phpunit/schema/10.5.xsd"
 
       - name: "Validate PHPUnit 10+ config for use with PHPUnit 11"
-        uses: phpcsstandards/xmllint-validate@v1
+        uses: phpcsstandards/xmllint-validate@0fd9c4a9046055f621fca4bbdccb8eab1fd59fdc # v1.0.1
         with:
           pattern: "phpunit.xml.dist"
           xsd-file: "vendor/phpunit/phpunit/phpunit.xsd"
@@ -118,7 +118,7 @@ jobs:
 
     steps:
       - name: Checkout code
-        uses: actions/checkout@v5
+        uses: actions/checkout@08c6903cd8c0fde910a37f88322edcfb5dd907a8 # v5.0.0
 
       # Updating the lists can fail intermittently, typically after Microsoft has released a new package.
       # This should not be blocking for this job, so ignore any errors from this step.
@@ -132,7 +132,7 @@ jobs:
 
       # Show XML violations inline in the file diff.
       - name: Enable showing XML issues inline
-        uses: korelstar/xmllint-problem-matcher@v1
+        uses: korelstar/xmllint-problem-matcher@1bd292d642ddf3d369d02aaa8b262834d61198c0 # v1.2.0
 
       # Check code-style consistency of the XSD and XML files.
       - name: Check XSD code style

.github/workflows/label-merge-conflicts.yml

@@ -22,7 +22,7 @@ jobs:
 
     steps:
       - name: Check PRs for merge conflicts
-        uses: eps1lon/actions-label-merge-conflict@v3
+        uses: eps1lon/actions-label-merge-conflict@1df065ebe6e3310545d4f4c4e862e43bdca146f0 # v3.0.3
         with:
           dirtyLabel: "Status: has merge conflict"
           repoToken: ${{ secrets.GITHUB_TOKEN }}

.github/workflows/quicktest.yml

@@ -27,7 +27,7 @@ jobs:
 
     steps:
       - name: Checkout code
-        uses: actions/checkout@v5
+        uses: actions/checkout@08c6903cd8c0fde910a37f88322edcfb5dd907a8 # v5.0.0
 
       # Updating the lists can fail intermittently, typically after Microsoft has released a new package.
       # This should not be blocking for this job, so ignore any errors from this step.
@@ -40,7 +40,7 @@ jobs:
         run: sudo apt-get install --no-install-recommends -y libxml2-utils
 
       - name: Install PHP
-        uses: shivammathur/setup-php@v2
+        uses: shivammathur/setup-php@ec406be512d7077f68eed36e63f4d91bc006edc4 # master
         with:
           php-version: ${{ matrix.php }}
           ini-values: error_reporting=-1, display_errors=On, display_startup_errors=On
@@ -49,7 +49,7 @@ jobs:
       # Install dependencies and handle caching in one go.
       # @link https://github.com/marketplace/actions/install-php-dependencies-with-composer
       - name: Install Composer dependencies
-        uses: "ramsey/composer-install@v3"
+        uses: "ramsey/composer-install@3cf229dc2919194e9e36783941438d17239e8520" # 3.1.1
         with:
           # Bust the cache at least once a month - output format: YYYY-MM.
           custom-cache-suffix: $(date -u "+%Y-%m")
@@ -120,7 +120,7 @@ jobs:
 
     steps:
       - name: Checkout code
-        uses: actions/checkout@v5
+        uses: actions/checkout@08c6903cd8c0fde910a37f88322edcfb5dd907a8 # v5.0.0
 
       # 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.
@@ -134,7 +134,7 @@ jobs:
           fi
 
       - name: Install PHP
-        uses: shivammathur/setup-php@v2
+        uses: shivammathur/setup-php@ec406be512d7077f68eed36e63f4d91bc006edc4 # master
         with:
           php-version: ${{ matrix.php }}
           ini-values: ${{ steps.set_ini.outputs.PHP_INI }}
@@ -150,7 +150,7 @@ jobs:
       # Install dependencies and handle caching in one go.
       # @link https://github.com/marketplace/actions/install-php-dependencies-with-composer
       - name: Install Composer dependencies
-        uses: "ramsey/composer-install@v3"
+        uses: "ramsey/composer-install@3cf229dc2919194e9e36783941438d17239e8520" # 3.1.1
         with:
           # Bust the cache at least once a month - output format: YYYY-MM.
           custom-cache-suffix: $(date -u "+%Y-%m")

.github/workflows/test.yml

@@ -30,7 +30,7 @@ jobs:
 
     steps:
       - name: Checkout code
-        uses: actions/checkout@v5
+        uses: actions/checkout@08c6903cd8c0fde910a37f88322edcfb5dd907a8 # v5.0.0
 
       # Updating the lists can fail intermittently, typically after Microsoft has released a new package.
       # This should not be blocking for this job, so ignore any errors from this step.
@@ -43,7 +43,7 @@ jobs:
         run: sudo apt-get install --no-install-recommends -y libxml2-utils
 
       - name: Install PHP
-        uses: shivammathur/setup-php@v2
+        uses: shivammathur/setup-php@ec406be512d7077f68eed36e63f4d91bc006edc4 # master
         with:
           php-version: ${{ matrix.php }}
           ini-values: error_reporting=-1, display_errors=On, display_startup_errors=On
@@ -53,7 +53,7 @@ jobs:
       # Install dependencies and handle caching in one go.
       # @link https://github.com/marketplace/actions/install-php-dependencies-with-composer
       - name: Install Composer dependencies
-        uses: "ramsey/composer-install@v3"
+        uses: "ramsey/composer-install@3cf229dc2919194e9e36783941438d17239e8520" # 3.1.1
         with:
           composer-options: ${{ matrix.php == '8.5' && '--ignore-platform-req=php+' || '' }}
           # Bust the cache at least once a month - output format: YYYY-MM.
@@ -174,7 +174,7 @@ jobs:
 
     steps:
       - name: Checkout code
-        uses: actions/checkout@v5
+        uses: actions/checkout@08c6903cd8c0fde910a37f88322edcfb5dd907a8 # v5.0.0
 
       - name: Setup ini config
         id: set_ini
@@ -188,7 +188,7 @@ jobs:
           fi
 
       - name: Install PHP
-        uses: shivammathur/setup-php@v2
+        uses: shivammathur/setup-php@ec406be512d7077f68eed36e63f4d91bc006edc4 # master
         with:
           php-version: ${{ matrix.php }}
           ini-values: ${{ steps.set_ini.outputs.PHP_INI }}
@@ -204,7 +204,7 @@ jobs:
       # Install dependencies and handle caching in one go.
       # @link https://github.com/marketplace/actions/install-php-dependencies-with-composer
       - name: Install Composer dependencies
-        uses: "ramsey/composer-install@v3"
+        uses: "ramsey/composer-install@3cf229dc2919194e9e36783941438d17239e8520" # 3.1.1
         with:
           composer-options: ${{ matrix.php == '8.5' && '--ignore-platform-req=php+' || '' }}
           # Bust the cache at least once a month - output format: YYYY-MM.

.github/workflows/update-website.yml

@@ -48,12 +48,12 @@ jobs:
           fi
 
       - name: Checkout code
-        uses: actions/checkout@v5
+        uses: actions/checkout@08c6903cd8c0fde910a37f88322edcfb5dd907a8 # v5.0.0
         with:
           ref: ${{ steps.base_branch.outputs.BRANCH }}
 
       - name: Install PHP
-        uses: shivammathur/setup-php@v2
+        uses: shivammathur/setup-php@ec406be512d7077f68eed36e63f4d91bc006edc4 # master
         with:
           php-version: 'latest'
           ini-values: error_reporting=-1, display_errors=On, display_startup_errors=On, log_errors_max_len=0
@@ -83,13 +83,13 @@ jobs:
           fi
 
       - name: Check GitHub Pages status
-        uses: crazy-max/ghaction-github-status@v4
+        uses: crazy-max/ghaction-github-status@fa6ac37620bc5d44b93e15caed498629665e9ff5 # v4.2.0
         with:
           pages_threshold: major_outage
 
       - name: Deploy the website
         if: success()
-        uses: crazy-max/ghaction-github-pages@v4
+        uses: crazy-max/ghaction-github-pages@df5cc2bfa78282ded844b354faee141f06b41865 # v4.2.0
         with:
           build_dir: 'deploy'
           target_branch: 'gh-pages'