I had only done the initial commit previously, and it was not there at that point. I was hoping to remove the reference before doing the next commit.

Thanks for the detailed explanation. I committed as you suggest, even though I was hoping to not have references to it in the repository. But its a new day, so when I started Xcode this morning, it had thankfully vanished. Problem avoided, but I have no idea why or how. You obviously have lots of experience and expertise with git, which I am still trying to master. Your command line suggestions are very welcome, since I have been simply using GitHub Desktop, and I have not seen similar options.