extract first port from Dockerfile and set config variable for use in deploy phase. closes #993

plugins/00_dokku-standard/commands

@@ -34,6 +34,9 @@ case "$1" in
         ;;
 
       dockerfile)
+        # extract first port from Dockerfile
+        DOCKERFILE_PORT=$(grep EXPOSE Dockerfile | head -1 | awk '{ print $2 }')
+        [[ -n "$DOCKERFILE_PORT" ]] && dokku config:set $APP DOKKU_DOCKERFILE_PORT=$DOCKERFILE_PORT
         # sticking with same pattern of building app image before pre-build for now.
         docker build -t "$IMAGE" .
         # buildstep pluginhooks don't necessarily make sense for dockerfiles. call the new breed!!!