Reconcile GitHub Actions with master

Roughty matches as of 9f2b9256b6.

Hopefully this makes CI work again.

.github/workflows/ci.yml

@@ -1,32 +1,49 @@
-name: "Test"
+name: "CI"
 
 on:
   pull_request:
   push:
 
+permissions: read-all
+
 jobs:
 
   tests:
     needs: [check_cachix]
     strategy:
+      fail-fast: false
       matrix:
         os: [ubuntu-latest, macos-latest]
     runs-on: ${{ matrix.os }}
     timeout-minutes: 60
     steps:
-    - uses: actions/checkout@v2.4.0
+    - uses: actions/checkout@v4
       with:
         fetch-depth: 0
-    - uses: cachix/install-nix-action@v16
+    - uses: cachix/install-nix-action@v30
+      with:
+        # The sandbox would otherwise be disabled by default on Darwin
+        extra_nix_config: |
+          sandbox = true
+          max-jobs = 1
     - run: echo CACHIX_NAME="$(echo $GITHUB_REPOSITORY-install-tests | tr "[A-Z]/" "[a-z]-")" >> $GITHUB_ENV
-    - uses: cachix/cachix-action@v10
+    - uses: cachix/cachix-action@v15
       if: needs.check_cachix.outputs.secret == 'true'
       with:
         name: '${{ env.CACHIX_NAME }}'
         signingKey: '${{ secrets.CACHIX_SIGNING_KEY }}'
         authToken: '${{ secrets.CACHIX_AUTH_TOKEN }}'
+    # Since ubuntu 22.30, unprivileged usernamespaces are no longer allowed to map to the root user:
+    # https://ubuntu.com/blog/ubuntu-23-10-restricted-unprivileged-user-namespaces
+    - run: sudo sysctl -w kernel.apparmor_restrict_unprivileged_userns=0
+      if: matrix.os == 'ubuntu-latest'
     - run: nix-build release.nix -A build.$(nix-instantiate --eval -E '(builtins.currentSystem)')
 
+  # Steps to test CI automation in your own fork.
+  # Cachix:
+  # 1. Sign-up for https://www.cachix.org/
+  # 2. Create a cache for $githubuser-nix-install-tests
+  # 3. Create a cachix auth token and save it in https://github.com/$githubuser/nix/settings/secrets/actions in "Repository secrets" as CACHIX_AUTH_TOKEN
   check_cachix:
     name: Cachix secret present for installer tests
     runs-on: ubuntu-latest
@@ -37,7 +54,8 @@ jobs:
         id: secret
         env:
           _CACHIX_SECRETS: ${{ secrets.CACHIX_SIGNING_KEY }}${{ secrets.CACHIX_AUTH_TOKEN }}
-        run: echo "::set-output name=secret::${{ env._CACHIX_SECRETS != '' }}"
+        run: |
+          echo "::set-output name=secret::${{ env._CACHIX_SECRETS != '' }}"
 
   installer:
     needs: [tests, check_cachix]
@@ -46,16 +64,19 @@ jobs:
     outputs:
       installerURL: ${{ steps.prepare-installer.outputs.installerURL }}
     steps:
-    - uses: actions/checkout@v2.4.0
+    - uses: actions/checkout@v4
       with:
         fetch-depth: 0
     - run: echo CACHIX_NAME="$(echo $GITHUB_REPOSITORY-install-tests | tr "[A-Z]/" "[a-z]-")" >> $GITHUB_ENV
-    - uses: cachix/install-nix-action@v16
+    - uses: cachix/install-nix-action@v30
-    - uses: cachix/cachix-action@v10
+      with:
+        install_url: https://releases.nixos.org/nix/nix-2.20.3/install
+    - uses: cachix/cachix-action@v15
       with:
         name: '${{ env.CACHIX_NAME }}'
         signingKey: '${{ secrets.CACHIX_SIGNING_KEY }}'
         authToken: '${{ secrets.CACHIX_AUTH_TOKEN }}'
+        cachixArgs: '-v'
     - id: prepare-installer
       run: scripts/prepare-installer-for-github-actions
 
@@ -63,13 +84,14 @@ jobs:
     needs: [installer, check_cachix]
     if: github.event_name == 'push' && needs.check_cachix.outputs.secret == 'true'
     strategy:
+      fail-fast: false
       matrix:
         os: [ubuntu-latest, macos-latest]
     runs-on: ${{ matrix.os }}
     steps:
-    - uses: actions/checkout@v2.4.0
+    - uses: actions/checkout@v4
     - run: echo CACHIX_NAME="$(echo $GITHUB_REPOSITORY-install-tests | tr "[A-Z]/" "[a-z]-")" >> $GITHUB_ENV
-    - uses: cachix/install-nix-action@v16
+    - uses: cachix/install-nix-action@v30
       with:
         install_url: '${{needs.installer.outputs.installerURL}}'
         install_options: "--tarball-url-prefix https://${{ env.CACHIX_NAME }}.cachix.org/serve"