Describe the bug

While looking through the code, I came across a few details that would be good to fix up.

modifies the local check-out, w/out undoing the changes.

modifies the environment of the tests w/out undoing the changes. Also seems to test a branch in the commit message generation that's not covered elsewhere, but also isn't part of the test description?

https://github.com/JamesIves/github-pages-deploy-action/blob/dev-v4/src/git.ts#L58 doesn't actually run the | wc -l part, as it's not a shell. Well, it runs it, in the sense that it just passes them as options to the git command.