% git grep -i --all-match -e "df.*-sh"
debian.txt:PDF Arranger was formerly known as PDF-Shuffler.

• https://amitness.com/regex/ - nice intro level tutorial on regex. It talks about regex first and then touches the functions in python's re module. Easy to read and follow along.
• regex cheatsheet - http://www.rexegg.com/regex-quickstart.html