ci: pin actions to commit SHAs and lint workflows

.github/dependabot.yml

@@ -4,6 +4,8 @@ updates:
     directory: "/"
     schedule:
       interval: "weekly"
+    cooldown:
+      default-days: 7
     groups:
       actions:
         patterns:

.github/pinact.yaml

@@ -0,0 +1,9 @@
+version: 3
+rules:
+  # Branch refs that must keep tracking their branch: there is no stable tag
+  # to pin to. lean-update's `dev` carries the fork's features, and the shared
+  # ci-workflows actions are consumed from `main`.
+  - ignore: true
+    conditions:
+      - expr: ActionName == "argumentcomputer/lean-update"
+      - expr: ActionName matches "^argumentcomputer/ci-workflows/"

.github/workflows/ci.yml

@@ -25,8 +25,10 @@ jobs:
     runs-on: runs-on=${{ github.run_id }}-build-${{ github.run_attempt }}/cpu=8/family=r7i+r8i+r7a+r8a/image=ubuntu26-full-x64/volume=100gb/sticky=ci-build:50gb
     timeout-minutes: 60
     steps:
-      - uses: actions/checkout@v7
-      - uses: runs-on/action@v2
+      - uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7.0.1
+        with:
+          persist-credentials: false
+      - uses: runs-on/action@dfae4d98c5537a0dc7bbb7e6b9211f30ba240f6d # v2.4.0
         with:
           sticky_cache: |
             custom,path=.lake
@@ -38,7 +40,7 @@ jobs:
       # the frontier `sorry`s are annotated at their declarations, so they no
       # longer count. `Lean4Lean.Experimental` is not a default target.
       - name: Build
-        uses: leanprover/lean-action@v1
+        uses: leanprover/lean-action@50fcf42d2e460296f1a34b402e990d1b24f8b596 # v1.6.0
         with:
           build-args: --wfail
           use-github-cache: false
@@ -79,3 +81,14 @@ jobs:
       # support loose bound variables" (digama0/lean4lean#17).
       - name: Recheck Init.System.IO and its imports from scratch
         run: lake exe lean4lean --fresh Init.System.IO
+
+  lints:
+    name: Lint workflows
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7.0.1
+        with:
+          persist-credentials: false
+      # actionlint, shellcheck over composite action scripts, pinact (actions
+      # must be SHA-pinned with a matching version comment) and zizmor
+      - uses: argumentcomputer/ci-workflows/.github/actions/lint-workflows@main

.github/workflows/nix.yml

@@ -23,12 +23,14 @@ jobs:
     # /nix lives on the root volume; Cachix is the binary cache, so no sticky disk
     runs-on: runs-on=${{ github.run_id }}-nix-test-${{ github.run_attempt }}/cpu=8/family=r7i+r8i+r7a+r8a/image=ubuntu26-full-x64/volume=100gb
     steps:
-      - uses: actions/checkout@v7
-      - uses: cachix/install-nix-action@v31
+      - uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7.0.1
+        with:
+          persist-credentials: false
+      - uses: cachix/install-nix-action@13d8dd58da0234aa297dedd986986ccb8e7f3e24 # v31.11.1
         with:
           nix_path: nixpkgs=channel:nixos-unstable
-          github_access_token: ${{ secrets.GITHUB_TOKEN }}
-      - uses: cachix/cachix-action@v17
+          github_access_token: ${{ github.token }}
+      - uses: cachix/cachix-action@38b082610b782e7e93e209c35fd730d399dee866 # v17
         with:
           name: argumentcomputer
           authToken: ${{ secrets.CACHIX_AUTH_TOKEN }}
@@ -47,16 +49,18 @@ jobs:
     # on a sticky disk like ci.yml's
     runs-on: runs-on=${{ github.run_id }}-nix-devshell-${{ github.run_attempt }}/cpu=8/family=r7i+r8i+r7a+r8a/image=ubuntu26-full-x64/volume=100gb/sticky=nix-devshell:50gb
     steps:
-      - uses: actions/checkout@v7
-      - uses: runs-on/action@v2
+      - uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7.0.1
+        with:
+          persist-credentials: false
+      - uses: runs-on/action@dfae4d98c5537a0dc7bbb7e6b9211f30ba240f6d # v2.4.0
         with:
           sticky_cache: |
             custom,path=.lake
-      - uses: cachix/install-nix-action@v31
+      - uses: cachix/install-nix-action@13d8dd58da0234aa297dedd986986ccb8e7f3e24 # v31.11.1
         with:
           nix_path: nixpkgs=channel:nixos-unstable
-          github_access_token: ${{ secrets.GITHUB_TOKEN }}
-      - uses: cachix/cachix-action@v17
+          github_access_token: ${{ github.token }}
+      - uses: cachix/cachix-action@38b082610b782e7e93e209c35fd730d399dee866 # v17
         with:
           name: argumentcomputer
           authToken: ${{ secrets.CACHIX_AUTH_TOKEN }}

.github/workflows/update.yml

@@ -17,12 +17,13 @@ jobs:
       # create-pull-request takes its base from the checked-out branch, and the
       # action passes no `base` of its own, so this is what points the update PR
       # at `main`, the default branch.
-      - uses: actions/checkout@v7
+      - uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7.0.1
         with:
           ref: main
+          persist-credentials: false
 
       # `update_lean4_nix` below runs `nix flake update`
-      - uses: cachix/install-nix-action@v31
+      - uses: cachix/install-nix-action@13d8dd58da0234aa297dedd986986ccb8e7f3e24 # v31.11.1
         with:
           github_access_token: ${{ github.token }}
 

.github/zizmor.yml

@@ -0,0 +1,8 @@
+rules:
+  unpinned-uses:
+    config:
+      policies:
+        # Branch-tracking refs allowed by .github/pinact.yaml
+        "argumentcomputer/lean-update": ref-pin
+        "argumentcomputer/ci-workflows/*": ref-pin
+        "*": hash-pin