On the GitHub side, everything will behave as if your new username had always been your name. All of your repositories will now belong to that new name and the old username will essentially no longer exist. This can take a few minutes to complete after you initiate the change.
Links to your previous profile page, such as
https://github.com/previoususername, return a 404 error. We cannot set up a redirect from the old username to the new one for references like @mentions.
However, redirects are setup for all your repositories. Both web and git access to the old location continue to function, and redirect toward the new username.
You should remember to update the remotes in your local repositories to point to the new location. You can use
git remote -v to see all the old remotes and look for references to your old username, then use
git remote set-url <name> <new-url> to update them.
Your Git history is not affected and commits are linked to your new username, so long as you don’t also change your email address.