Fatal: A branch named 'gh-pages' already exists.

A small attempt to save someone else some headscratching and pain over this silly little error.

Early on in developing this site, I was using the gh-pages npm package to do some preliminary deployments of the site, just to get the plumbing all working.

The problem

My deploy script in my package.json looks like this:

  "scripts": {
    "deploy": "gatsby build && gh-pages -d public",
    ...
  }

but running it produced the error:

fatal: A branch named 'gh-pages' already exists.

It just made no sense.

The fix

The simple fix was clearing out the gh-pages cache in node_modules:

# from project root
$ rm -rf node_modules/.cache/gh-pages/

Turns out to be some bug in the way gh-pages caches builds or assets. I had too many things to do to dig in further but hopefully this helps someone.