docs: add Netlify configuration for docs hosting migration

docs/.gitignore

@@ -20,3 +20,6 @@ node_modules/
 
 # Hugo
 .hugo_build.lock
+
+# Netlify CLI (auto-generated, contains local paths)
+.netlify/

docs/README.md

@@ -4,7 +4,7 @@ The source files for the documentation are located in the [content](https://gith
 
 # Website
 
-The PipeCD documentation website is built with [Hugo](https://gohugo.io/) and published at https://pipecd.dev
+The PipeCD documentation website is built with [hugo](https://gohugo.io/) and hosted on [Netlify](https://www.netlify.com/), published at https://pipecd.dev
 
 # Docs workflow and versioning
 
@@ -26,18 +26,37 @@ Here are the recommended flows for common documentation updates:
 
 If you find any issues related to the docs, we're happy to accept your help.
 
-# How to run the website locally
+# Hosting
+
+The site is hosted on Netlify with the following setup:
+- **Build tool**: Hugo (extended) via `netlify.toml` configuration
+- **Deploy trigger**: Automatic on push to `master` branch and version tags
+- **Deploy previews**: Automatically generated for pull requests that modify `docs/`
+- **Redirects**: `/docs/` redirects to the latest released version (configured in `netlify.toml`)
+
+# How to run website locally
 
 ## Prerequisite
 - [Hugo 0.148.2+extended](https://gohugo.io/)
+- [Node.js 24+](https://nodejs.org/)
 
 ## Commands
-
-Run `make run/site` at the root directory of the repository and then access http://localhost:1313
-
-> **Note for Windows users:**
-> The `make run/site` command uses `make` and `grep`, which are not natively available in Windows PowerShell. You can either use an environment like WSL or run the Hugo command manually in PowerShell:
-> ```powershell
-> $env:RELEASE = (Select-String -Path RELEASE -Pattern "^tag:").Line.Split(":")[1].Trim()
-> hugo server --source=docs
-> ```
+1. Install Hugo theme dependencies:
+```
+cd docs && npm install
+```
+2. Run the development server:
+```
+hugo server
+```
+3. Access http://localhost:1313
+
+# Netlify Configuration
+
+The Netlify build configuration is defined in [`netlify.toml`](./netlify.toml). Key settings:
+- **Build command**: `npm ci && hugo --gc --minify`
+- **Publish directory**: `public/`
+- **Redirects**: `/docs/` → latest version docs
+- **Security headers**: X-Frame-Options, X-XSS-Protection, etc.
+
+When a new release version is created, the `hack/gen-release-docs.sh` script automatically updates the redirect target in `netlify.toml`.

docs/netlify.toml

@@ -0,0 +1,54 @@
+# Netlify configuration for PipeCD documentation site.
+# Ref: https://docs.netlify.com/configure-builds/file-based-configuration/
+
+[build]
+  # Build command reads the RELEASE tag from the root RELEASE file
+  # and passes it as an env var to Hugo (used by the latest_version shortcode).
+  command = "npm ci && RELEASE=$(grep '^tag:' ../RELEASE | awk '{print $2}') hugo --gc --minify"
+  publish = "public"
+
+[build.environment]
+  HUGO_VERSION = "0.148.2"
+  HUGO_ENV = "production"
+  NODE_VERSION = "24"
+
+# Redirect /docs/ to the latest released version.
+# Don't update here manually. hack/gen-release-docs.sh does.
+[[redirects]]
+  from = "/docs/*"
+  to = "/docs-v1.0.x/:splat"
+  status = 302
+  force = true
+
+# Redirect /docs (without trailing slash) as well.
+[[redirects]]
+  from = "/docs"
+  to = "/docs-v1.0.x/"
+  status = 302
+  force = true
+
+# Custom 404 page.
+[[redirects]]
+  from = "/*"
+  to = "/404.html"
+  status = 404
+
+# Headers for security and caching.
+[[headers]]
+  for = "/*"
+  [headers.values]
+    X-Frame-Options = "DENY"
+    X-XSS-Protection = "1; mode=block"
+    X-Content-Type-Options = "nosniff"
+    Referrer-Policy = "strict-origin-when-cross-origin"
+
+# Cache static assets aggressively.
+[[headers]]
+  for = "/images/*"
+  [headers.values]
+    Cache-Control = "public, max-age=31536000, immutable"
+
+[[headers]]
+  for = "/favicons/*"
+  [headers.values]
+    Cache-Control = "public, max-age=31536000, immutable"

hack/gen-release-docs.sh

@@ -65,4 +65,10 @@ mv docs/config.toml.tmp docs/config.toml
 sed "s/const latestPath.*/const latestPath = \"\/docs-"$VERSION"\/\"/g" docs/main.go > docs/main.go.tmp
 mv docs/main.go.tmp docs/main.go
 
+# Update docs/netlify.toml redirect to point to new latest version
+sed "s|to = \"/docs-.*/:splat\"|to = \"/docs-$VERSION/:splat\"|g" docs/netlify.toml > docs/netlify.toml.tmp
+mv docs/netlify.toml.tmp docs/netlify.toml
+sed "s|to = \"/docs-.*/\"|to = \"/docs-$VERSION/\"|g" docs/netlify.toml > docs/netlify.toml.tmp
+mv docs/netlify.toml.tmp docs/netlify.toml
+
 echo "Version docs has been prepared successfully at $CONTENT_DIR/docs-$VERSION/"