use the node hostname as a config name when available

Procfile

@@ -1,3 +1,3 @@
 swarmmerge: while true; do ls -d /etc/nginx/node.conf.d/*.conf | entr -d python3 /app/mergeswarm.py; done
-dockergen: docker-gen -watch /app/nginx.tmpl /etc/nginx/node.conf.d/`hostname`.conf
+dockergen: docker-gen -watch /app/nginx.tmpl /etc/nginx/node.conf.d/${NODE_HOSTNAME:-`hostname`}.conf
 nginx: nginx

swarm.stack.yml

@@ -12,6 +12,8 @@ services:
             - proxy
         ports:
             - "80:80"
+        environment:
+            - NODE_HOSTNAME={{.Node.Hostname}}
         volumes:
             - /var/run/docker.sock:/tmp/docker.sock:ro
             - /tmp/proxyconf/:/etc/nginx/node.conf.d/