From ed25c62fed56b11aa7feb6dc1231312af6995cc6 Mon Sep 17 00:00:00 2001
From: Zaiming Shi <zmstone@gmail.com>
Date: Wed, 20 Jan 2021 12:37:21 +0100
Subject: [PATCH] chore(elvis): Add usage print

---
 scripts/elvis-check.sh | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/scripts/elvis-check.sh b/scripts/elvis-check.sh
index 7ba8b72eb..0e105bf99 100755
--- a/scripts/elvis-check.sh
+++ b/scripts/elvis-check.sh
@@ -1,10 +1,18 @@
 #!/bin/bash
 
+## This script checks style of changed files.
+## Expect argument 1 to be the git compare base.
+
 set -euo pipefail
 
 ELVIS_VERSION='1.0.0-emqx-1'
 
-base="${GITHUB_BASE_REF:-$1}"
+base="${1:-}"
+if [ "${base}" = "" ]; then
+    echo "Usage $0 <git-compare-base-ref>"
+    exit 1
+fi
+
 elvis_version="${2:-$ELVIS_VERSION}"
 
 echo "elvis -v: $elvis_version"