By google-ing, we'd find a simple command as git branch -m master main which should rename the master branch to main.

What if it was not successful and you had,

error: refname refs/heads/master not found
fatal: Branch rename failed

Well, in my case, I create a new project then I initialized git. I then remembered that by default, on Github, the default branch is main and not master anymore.

You can change the name from master to main in few steps, locally before you even make a commit.

1. Navigate to the directory where your project sits.
2. In it, show hidden file since by default, .git would be hidden.
3. Inside .git, there is a file, HEAD, open it in a text editor. You'd see, ref: refs/heads/master.
4. Simple enough, change, master to main.

We just renamed the master branch as main. Verify this merely by entering, git branch from the terminal.

In an instance where the project is new locally (the project is git initialized locally), then after the first commit, git add . && git commit -m "Initial commit" we can rename the current branch with, git branch -m main`.