change repo default branch code example

Example 1: change default branch github

On GitHub, navigate to the main page of the repository.
Under your repository name, click Settings.
In the left menu, click Branches.
Under "Default branch", to the right of the default branch name, click .
Use the drop-down, then click a branch name.
Click Update.

Example 2: Change default branch on git

git branch -m deploy prod
git fetch origin
git branch -u origin/prod prod
git remote set-head origin -a