ci: Port CI to just

.github/actions/cache_restore/action.yml

@@ -0,0 +1,21 @@
+name: cache_restore
+runs:
+  using: composite
+  steps:
+    - uses: actions/cache/restore@v4
+      with:
+        path: |
+          # See https://doc.rust-lang.org/cargo/guide/cargo-home.html#caching-the-cargo-home-in-ci
+          ~/.cargo/.crates.toml
+          ~/.cargo/.crates2.json
+          ~/.cargo/bin/
+          ~/.cargo/registry/index/
+          ~/.cargo/registry/cache/
+          ~/.cargo/git/db/
+          # See https://doc.rust-lang.org/cargo/guide/build-cache.html
+          target
+        key: ${{ runner.os }}|${{ github.job }}|${{ github.run_attempt }}
+        restore-keys: |
+          ${{ runner.os }}|${{ github.job }}
+          ${{ runner.os }}
+

.github/actions/cache_save/action.yml

@@ -0,0 +1,18 @@
+name: cache_save
+runs:
+  using: composite
+  steps:
+    - uses: actions/cache/save@v4
+      with:
+        path: |
+          # See https://doc.rust-lang.org/cargo/guide/cargo-home.html#caching-the-cargo-home-in-ci
+          ~/.cargo/.crates.toml
+          ~/.cargo/.crates2.json
+          ~/.cargo/bin/
+          ~/.cargo/registry/index/
+          ~/.cargo/registry/cache/
+          ~/.cargo/git/db/
+          # See https://doc.rust-lang.org/cargo/guide/build-cache.html
+          target
+        key: ${{ runner.os }}|${{ github.job }}|${{ github.run_attempt }}
+

.github/workflows/audit.yml

@@ -1,15 +1,35 @@
-name: Audit
-
+name: audit
 on:
+  push:
+    branches: [ main ]
+    paths:
+      - "**.rs"
+      - "**.toml"
+      - ".github/workflows/**"
+  pull_request:
+    branches: [ main ]
+    paths:
+      - "**.rs"
+      - "**.toml"
+      - ".github/workflows/**"
   schedule:
     # 21:43 on Wednesday and Sunday. (Thanks, crontab.guru)
-    - cron: "43 21 * * 3,0"
+    - cron: '43 21 * * 3,0'
   workflow_dispatch:
 
+concurrency:
+  group: ${{ github.workflow }}-${{ github.ref }}
+  cancel-in-progress: true
+
 jobs:
   audit:
     runs-on: ubuntu-latest
 
     steps:
       - uses: actions/checkout@v4
-      - uses: EmbarkStudios/cargo-deny-action@1e59595bed8fc55c969333d08d7817b36888f0c5
+
+      - uses: ./.github/actions/cache_restore
+      - run: cargo install just
+      - run: just audit
+      - uses: ./.github/actions/cache_save
+