Add circleci

.circleci/config.yml

@@ -0,0 +1,8 @@
+version: 2.1
+orbs:
+  shellcheck: circleci/shellcheck@2.2.4
+workflows:
+  check-scripts:
+    jobs:
+      - shellcheck/check:
+          dir: ./scripts

scripts/upgrade-from-mattermost-docker.sh

@@ -1,6 +1,6 @@
-#!/bin/bash
+#!/usr/bin/env bash
 
-set -e
+set -o errexit
 
 ##
 ## Instructions