perf: build docs on the CI runner with a warm .next cache (#840)

Move `npm run build` out of the Docker image onto the runner, where actions/cache persists .next/cache across runs (the in-Docker build discarded it every time). The image now just packages the prebuilt .next and serves it with `next start`; runtime and the DocSearch entrypoint injection are unchanged.

Also: checkout full history (fetch-depth: 0) so per-page dates are correct, guard buildGitDateMap against shallow clones (correct-or-absent, never wrong), modernise the Docker actions (build-push-action v6, provenance: false), and add a path-filtered pull_request trigger so pipeline changes are validated before merge.

Smoke-tested via isolated build + docker run: serves /, /introduction, /api, sitemap, static assets (200); DocSearch placeholder injection intact.

.dockerignore

@@ -1,10 +1,15 @@
 .git/
 .gitignore
-.next/                # Existing Next.js builds
 .dockerignore
 Dockerfile
 docker-compose.yml
-node_modules/         # Installed inside container
 LICENSE
 README.md
-AUTHORS
+AUTHORS
+
+# Reinstalled inside the image (alpine-native — avoids a glibc/musl mismatch)
+node_modules/
+
+# The built .next output is copied in (built on the CI runner, see
+# build_n_push.yml); only the build cache is excluded — it is not served.
+.next/cache/

.github/workflows/build_n_push.yml

@@ -3,31 +3,66 @@ on:
   push:
     branches:
       - main
+  # Build-only (no push) on PRs that touch the build/deploy pipeline, so
+  # Dockerfile / workflow changes are validated before they reach main.
+  pull_request:
+    paths:
+      - 'docker/**'
+      - '.github/workflows/build_n_push.yml'
+      - 'next.config.mjs'
+      - 'package-lock.json'
   workflow_dispatch:
-  
+
 jobs:
   docs_build_n_push:
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v2
-      -
-        name: Docker meta
+      - uses: actions/checkout@v4
+        with:
+          # Full history so gen:last-updated / gen:sitemap can read real
+          # per-file commit dates (a shallow clone would yield wrong dates).
+          fetch-depth: 0
+
+      - uses: actions/setup-node@v4
+        with:
+          node-version: '20'
+          cache: 'npm'
+
+      - name: Install dependencies
+        run: npm ci
+
+      - name: Restore Next.js build cache
+        uses: actions/cache@v4
+        with:
+          path: .next/cache
+          key: ${{ runner.os }}-nextjs-${{ hashFiles('package-lock.json') }}-${{ hashFiles('src/**', 'mdx/**', 'next.config.mjs') }}
+          restore-keys: |
+            ${{ runner.os }}-nextjs-${{ hashFiles('package-lock.json') }}-
+
+      - name: Build
+        run: npm run build
+
+      - name: Docker meta
         id: meta
-        uses: docker/metadata-action@v3
+        uses: docker/metadata-action@v5
         with:
           images: netbirdio/docs.netbird.io
-      -
-        name: Login to DockerHub
+
+      - name: Login to DockerHub
         if: github.event_name != 'pull_request'
-        uses: docker/login-action@v1
+        uses: docker/login-action@v3
         with:
           username: ${{ secrets.DOCKER_USER }}
           password: ${{ secrets.DOCKER_TOKEN }}
-      -
-        name: Docker build and push
-        uses: docker/build-push-action@v2
+
+      - name: Docker build and push
+        uses: docker/build-push-action@v6
         with:
+          context: .
           file: docker/Dockerfile
           push: ${{ github.event_name != 'pull_request' }}
+          # Keep a single-arch manifest (no attestation index) so the server's
+          # `docker compose pull` stays happy.
+          provenance: false
           tags: ${{ steps.meta.outputs.tags }}
           labels: ${{ steps.meta.outputs.labels }}

docker/Dockerfile

@@ -10,17 +10,16 @@ RUN npm install --global pm2
 # Utilise Docker cache to save re-installing dependencies if unchanged
 COPY ./package*.json ./
 
-# Install dependencies (npm ci = clean, reproducible install from the lockfile)
+# Install runtime dependencies (npm ci = clean, reproducible install from the lockfile)
 RUN npm ci --omit=dev
 
-# Copy all files
+# Copy the app, including the prebuilt .next output. The build now runs on the
+# CI runner (see .github/workflows/build_n_push.yml) with a warm .next/cache,
+# so there is no `npm run build` step here — we only package the result.
 COPY ./ ./
 
 COPY /docker/entrypoint.sh ./entrypoint.sh
 
-# Build app
-RUN npm run build
-
 RUN chmod u+x /usr/app/entrypoint.sh
 
 # Expose the listening port

scripts/git-dates.mjs

@@ -32,13 +32,24 @@ let _dateMapCache
  * repo-relative with forward slashes, matching path.relative(repoRoot, file).
  *
  * Returns an empty map if git is unavailable (e.g. inside the Docker image,
- * which has no git binary); callers then fall back to no date, exactly as the
- * per-file getGitLastModified() did.
+ * which has no git binary) or the checkout is shallow; callers then fall back
+ * to no date, exactly as the per-file getGitLastModified() did.
  */
 export function buildGitDateMap() {
   if (_dateMapCache) return _dateMapCache
   const map = new Map()
   try {
+    // On a shallow clone (e.g. actions/checkout without fetch-depth: 0) git log
+    // only sees the fetched commits, so every file would report the same wrong
+    // date. Emit no dates rather than wrong ones.
+    const shallow = execSync('git rev-parse --is-shallow-repository', {
+      encoding: 'utf-8',
+      stdio: ['pipe', 'pipe', 'ignore'],
+    }).trim()
+    if (shallow === 'true') {
+      _dateMapCache = map
+      return map
+    }
     // core.quotePath=false keeps non-ASCII paths unquoted so line parsing is safe.
     const out = execSync(
       'git -c core.quotePath=false log --format=%cI --name-only',