Add SHARELATEX_PORT option, default to 80

This allows a user to configure the host port that the sharelatex
container will bind to. Previously this was hard-coded to port 80, which
can cause problems on systems with something already bound to that port.

bin/docker-compose

@@ -84,6 +84,7 @@ function __main__() {
   # Export vars for use in docker-compose files
   export IMAGE="$full_image_spec"
   export SHARELATEX_DATA_PATH
+  export SHARELATEX_PORT
   export DOCKER_SOCKET_PATH
   export MONGO_IMAGE
   export MONGO_DATA_PATH

lib/config-seed/overleaf.rc

@@ -5,6 +5,7 @@ PROJECT_NAME=overleaf
 # Sharelatex container
 SHARELATEX_DATA_PATH=data/sharelatex
 SERVER_PRO=false
+SHARELATEX_PORT=80
 
 # Sibling Containers
 SIBLING_CONTAINERS_ENABLED=false

lib/docker-compose.base.yml

@@ -9,7 +9,7 @@ services:
         volumes:
             - "${SHARELATEX_DATA_PATH}:/var/lib/sharelatex"
         ports:
-            - 80:80
+            - "${SHARELATEX_PORT:-80}:80"
         environment:
           SHARELATEX_MONGO_URL: "${MONGO_URL}"
           SHARELATEX_REDIS_HOST: "${REDIS_HOST}"