warn when stopping proxy when the env is using it

weave

@@ -1022,6 +1022,12 @@ proxy_addr() {
     fi
 }
 
+warn_if_stopping_proxy_in_env() {
+    if PROXY_ADDR=$(proxy_addr 2>/dev/null) ; then
+        [ "$PROXY_ADDR" != "$DOCKER_CLIENT_HOST" ] || echo "WARNING: It appears that your environment is configured to use the Weave Docker API proxy. Stopping it will break this and subsequent docker invocations. To restore your environment, run '\$(eval weave env --restore)'."
+    fi
+}
+
 ######################################################################
 # launch helpers
 ######################################################################
@@ -1503,6 +1509,7 @@ case "$COMMAND" in
         ;;
     stop)
         [ $# -eq 0 ] || usage
+        warn_if_stopping_proxy_in_env
         stop $PROXY_CONTAINER_NAME "Proxy"
         stop $CONTAINER_NAME       "Weave"
         conntrack -D -p udp --dport $PORT >/dev/null 2>&1 || true
@@ -1514,6 +1521,7 @@ case "$COMMAND" in
         ;;
     stop-proxy)
         [ $# -eq 0 ] || usage
+        warn_if_stopping_proxy_in_env
         stop $PROXY_CONTAINER_NAME "Proxy"
         ;;
     reset)