runner: Caddyfile for cache HTTPS frontend + README

runner/Caddyfile.example

@@ -0,0 +1,28 @@
+# Caddy snippet that serves the cargoxx binary cache over HTTPS.
+# Append to /etc/caddy/Caddyfile (or include via `import`) and reload:
+#   sudo systemctl reload caddy
+#
+# Caddy handles cert provisioning + renewal via ACME automatically.
+# Adjust the domain + the `root` path if the runner lives elsewhere.
+#
+# The cache is read-only here — writes happen exclusively from the
+# runner job container (`nix copy --to file:///srv/cargoxx-cache/store`).
+
+cache.cargoxx.amadey.xyz {
+	root * /home/mozart/cargoxx-pkgs/runner/cache/store
+	file_server browse=false
+
+	# narinfo / nar are immutable per content hash → cache aggressively.
+	@cache_immutable path *.narinfo *.nar.xz *.nar
+	header @cache_immutable Cache-Control "public, immutable, max-age=31536000"
+
+	# Substituter probe — short cache, must reflect new entries quickly.
+	@cache_info path /nix-cache-info
+	header @cache_info Cache-Control "public, max-age=300"
+
+	# Logs go to /var/log/caddy/cargoxx-cache.{access,error}.log by
+	# default; uncomment to override.
+	# log {
+	#     output file /var/log/caddy/cargoxx-cache.log
+	# }
+}

runner/README.md

@@ -61,22 +61,20 @@ Self-hosted Gitea Actions runner that validates package PRs.
    The `cache/` directory is gitignored. Both keys live alongside
    `compose.yml`; the named volume binds use `${PWD}/cache/...`.
 
-5. **(optional) Front the store with nginx** so substituters can read it:
+5. **(optional) Front the store with Caddy** so substituters can read it.
+   A ready-to-edit `Caddyfile.example` ships in this directory — copy
+   into `/etc/caddy/Caddyfile` (or `import` it) and reload:
 
-   ```nginx
-   # /etc/nginx/sites-available/cargoxx-cache
-   server {
-       listen 443 ssl;
-       server_name cache.cargoxx.<your-domain>;
-       root /path/to/cargoxx-pkgs/runner/cache/store;
-       autoindex off;
-       location / { try_files $uri =404; }
-   }
+   ```sh
+   sudo install -m644 Caddyfile.example /etc/caddy/conf.d/cargoxx-cache
+   sudo systemctl reload caddy
    ```
 
-   Consumers later need `substituters = https://cache.cargoxx.<your-domain>`
-   and `trusted-public-keys = <contents of cache.pub>` in their nix
-   config (bake this into the cargoxx wrapper once ready).
+   Caddy auto-provisions a Let's Encrypt cert. Consumers later need
+   `substituters = https://cache.cargoxx.<your-domain>` and
+   `trusted-public-keys = <contents of cache.pub>` in their nix config
+   — those go into the cargoxx wrapper (`cargoxx`'s own `flake.nix`),
+   so any user installing the bundled cargoxx picks them up.
 
 6. **Start the runner**: