GH Actions: do not persist credentials

> By default, using `actions/checkout` causes a credential to be persisted in the checked-out repo's `.git/config`, so that subsequent `git` operations can be authenticated.
>
> Subsequent steps may accidentally publicly persist `.git/config`, e.g. by including it in a publicly accessible artifact via `actions/upload-artifact`.
>
> However, even without this, persisting the credential in the `.git/config` is non-ideal unless actually needed.
>
> **Remediation**
>
> Unless needed for `git` operations, `actions/checkout` should be used with `persist-credentials: false`.
>
> If the persisted credential is needed, it should be made explicit with `persist-credentials: true`.

This has now been addressed in all workflows.

Refs:
* https://unit42.paloaltonetworks.com/github-repo-artifacts-leak-tokens/
* https://docs.zizmor.sh/audits/#artipacked

Author: jrfnl

.github/workflows/basics.yml

@@ -26,6 +26,8 @@ jobs:
     steps:
       - name: Checkout code
         uses: actions/checkout@08c6903cd8c0fde910a37f88322edcfb5dd907a8 # v5.0.0
+        with:
+          persist-credentials: false
 
       - name: Install PHP
         uses: shivammathur/setup-php@ec406be512d7077f68eed36e63f4d91bc006edc4 # 2.35.4
@@ -110,6 +112,8 @@ jobs:
     steps:
       - name: Checkout code
         uses: actions/checkout@08c6903cd8c0fde910a37f88322edcfb5dd907a8 # v5.0.0
+        with:
+          persist-credentials: false
 
       # 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.

.github/workflows/quicktest.yml

@@ -46,6 +46,8 @@ jobs:
     steps:
       - name: Checkout code
         uses: actions/checkout@08c6903cd8c0fde910a37f88322edcfb5dd907a8 # v5.0.0
+        with:
+          persist-credentials: false
 
       - name: Install PHP
         uses: shivammathur/setup-php@ec406be512d7077f68eed36e63f4d91bc006edc4 # 2.35.4

.github/workflows/test.yml

@@ -34,6 +34,8 @@ jobs:
     steps:
       - name: Checkout code
         uses: actions/checkout@08c6903cd8c0fde910a37f88322edcfb5dd907a8 # v5.0.0
+        with:
+          persist-credentials: false
 
       - name: Install PHP
         uses: shivammathur/setup-php@ec406be512d7077f68eed36e63f4d91bc006edc4 # 2.35.4
@@ -132,6 +134,8 @@ jobs:
     steps:
       - name: Checkout code
         uses: actions/checkout@08c6903cd8c0fde910a37f88322edcfb5dd907a8 # v5.0.0
+        with:
+          persist-credentials: false
 
       # 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.
@@ -235,6 +239,8 @@ jobs:
     steps:
       - name: Checkout code
         uses: actions/checkout@08c6903cd8c0fde910a37f88322edcfb5dd907a8 # v5.0.0
+        with:
+          persist-credentials: false
 
       - name: Install PHP
         uses: shivammathur/setup-php@ec406be512d7077f68eed36e63f4d91bc006edc4 # 2.35.4