Include a custom nginx config fragment with NGINX_INCLUDE_FILE (#79)

* Refactor common config out of nginx templates.

* A way to inject custom nginx directives.

Setting the ENV variable `NGINX_INCLUDE_FILE` allows the user to specify a
file, relative to the app folder, which will be inserted into the nginx
server config.

This is useful for e.g. overriding a variable. For example to allow
uploads larger than 1Mb the user could create a file called `nginx.conf`
in their app repo containing: `client_max_body_size 8M;` and then set
`NGINX_INCLUDE_FILE=nginx.conf` in the ENV file.

This builds on #77 so that should be merged first.

docs/ENV.md

@@ -36,4 +36,5 @@ You can configure deployment settings by placing special variables in an `ENV` f
 * `NGINX_CLOUDFLARE_ACL` (boolean): activate an ACL allowing access only from Cloudflare IPs
 * `NGINX_STATIC_PATHS`: set an array of `/url:path` values
 * `NGINX_HTTPS_ONLY`: tell nginx to auto-redirect non-SSL traffic to SSL site
+* `NGINX_INCLUDE_FILE`: a file in the app's dir to include in nginx config `server` section - useful for including custom nginx directives.
 * `NGINX_ALLOW_GIT_FOLDERS`: (boolean) allow access to `.git` folders (default: false, blocked)

piku.py

@@ -117,6 +117,8 @@ NGINX_COMMON_FRAGMENT = """
   # set a custom header for requests
   add_header X-Deployed-By Piku;
 
+  $NGINX_CUSTOM_CLAUSES
+
   $INTERNAL_NGINX_STATIC_MAPPINGS
 
   $NGINX_BLOCK_GIT
@@ -619,6 +621,7 @@ def spawn_app(app, deltas={}):
                     echo("Error {} in static path spec: should be /url1:path1[,/url2:path2], ignoring.".format(e))
                     env['INTERNAL_NGINX_STATIC_MAPPINGS'] = ''
 
+            env['NGINX_CUSTOM_CLAUSES'] = expandvars(open(join(app_path, env["NGINX_INCLUDE_FILE"])).read(), env) if env.get("NGINX_INCLUDE_FILE") else ""
             env['NGINX_COMMON'] = expandvars(NGINX_COMMON_FRAGMENT, env)
 
             echo("-----> nginx will map app '{}' to hostname '{}'".format(app, env['NGINX_SERVER_NAME']))