Changing github repo branches from master to main

Naming the main branch master has always felt a bit weird. Rightly, there is recognition, triggered by the BLM movement, this should change to main.

I think new repositories on GitHub now default to main but that doesn't fix all the existing repos. Luckily it is easy enough to change the name of the main branch. Steven Mortimor has an easy to follow 5 step tutorial.