You've made the switch. You are now using neovim for all your text editing, and you've hardly even noticed that you aren't using regular old vim. Except one thing. Your git difftool and mergetool aren't quite right. One of two things is happening. Either you are using old vim (which is fine, but you want to switch completely to neovim) or things are breaking because you have gone so far as to not just install neovim but to also remove vim!
So why is this happening? Your git mergetool is still set to vim even
though you set your core.editor to nvim. So, we just tell git to use
for your mergetool.
First, you probably have or want something like this:
git config --global merge.tool vimdiff
vimdiff in there is not the
vimdiff executable. It refers to a
built-in script. There's also
vimdiff3. (3 is the best by
the way.) Those built-in scripts call the
merge_tool_path executable. Which
will be set to
vim by default. You can change that with
git config --global mergetool.path nvim
All done. The difftool uses the mergetool by default so that's all you need to set!