I was pushing and pulling from git in Terminal then I changed my username on github.com. I went to push some changes and it couldn\'t push because it was still recognizing
usually the user name resides under git config
git config --global user.name "first last"
although if you still see above doesn't work you could edit .gitconfig under your user directory of mac and update
[user] name = gitusername email = xyz@xyz.com