Make Git always use main as default branch

Git 2.28.0

git config --global init.defaultBranch main

Pre-Git 2.28.0

mkdir -p ~/.config/git/templates/default
echo "ref: refs/heads/main" > ~/.config/git/templates/default/HEAD
git config --global init.templateDir '~/.config/git/templates/default'

Make main your main

git branch -m master main && git push -u origin main

Next, tell GitHub or whoever your new default is main. Then you can tell the remote repo to destroy the old branch:

git push origin :master