shell script to output list of Jira tickets based on git commit history

gjt.sh

#!/usr/bin/env bash

# Git Jira Tickets
# Outputs a list of Jira ticket numbers from a git log

# Usage: gjt <since_commit>

commit_messages=$(git log --merges --pretty=format:'%h %s' $1^..HEAD | sed "s/ /SPACE_DELIMITER/g")

lines=()
i=0
for msg in $commit_messages;
do
  hash=$(echo $msg | egrep -o "^[a-f0-9]+")
  branch=$(echo $msg | egrep -o "(branch|from)SPACE_DELIMITER'?[a-zA-Z0-9/_-]+'?" | sed -E "s/branch|from|SPACE_DELIMITER|'//g")
  ticket=$(echo $msg | egrep -o "\[?[a-zA-Z]{2}-[0-9]+\]?" | sed 's/[][]//g' | tr [a-z] [A-Z])
  lines[$i]="- [[$ticket](https://salido.atlassian.net/browse/$ticket)] $hash $branch"
  ((i++))
done

printf "%s\n" "${lines[@]}" | sort -f