How to change a branch name in Git

git checkout -b trunk master # Create and switch to the trunk branch
git push -u origin trunk     # Push the trunk branch to the remote and
                             # track it
git branch -d master         # Delete local master
 
# Log into Bitbucket, go to the "Repository settings", and change the
# "Main branch" from "master" to "trunk".
#
git push --delete origin master # Delete remote master
git remote prune origin         # Delete the remote tracking branch

NOTE

GitHub deciding to switch “master” to “main” makes no sense to me. We talk about git “branches” and working “trees”. Shouldn’t the central branch in a git tree be the “trunk”?