scripts: fix authors script to take a ref (tendermint#7051)

This script is referenced from the release documentation, we should make sure it's functional. This is helpful in generating the "Special Thanks" section of the changelog.

scripts/authors.sh

@@ -1,16 +1,16 @@
 #! /bin/bash
 
-# Usage:
-#   `./authors.sh`
-#		Print a list of all authors who have committed to develop since master.
-#
-#   `./authors.sh <email address>`
-#		Lookup the email address on Github and print the associated username
+set -euo pipefail
 
-author=$1
+ref=$1
 
-if [[ "$author" == "" ]]; then
-	git log master..develop | grep Author | sort | uniq
+if [[ ! -z "$ref" ]]; then
+	git log master..$ref | grep Author | sort | uniq
 else
-	curl -s "https://api.github.com/search/users?q=$author+in%3Aemail&type=Users&utf8=%E2%9C%93" | jq .items[0].login
+cat << EOF
+Usage:
+	./authors.sh <ref>
+		Print a list of all authors who have committed to the codebase since the supplied commit ref. 
+EOF
 fi
+