Minimize repo clones

[christopher-dG]

With these changes, the repo isn't cloned if there are no new versions.

I'm currently looking at eliminating the clone for "new" releases that have already been handled by TagBot, but it's a bit tougher.

[christopher-dG]

There, now we should only ever clone when actually making a release.

[christopher-dG]

So this does work, but I've been looking into how the "official" actions/checkout does their cloning, and they do a more complex version of:

git init
git remote add origin ...
git fetch origin
git checkout <branch>

Presumably this doesn't add to the clone counter? I might give this a try, I think it would be nicer this way. Working with the local repo is a lot less error-prone than doing stuff over the network.

[christopher-dG]

I'm like 95% sure that this will avoid updating the clone graphs. I did a little experiment on a repo of my own, whenever GitHub updates the graphs I'll know for sure. This is definitely 500x simpler than the other solution.

[christopher-dG]

Rats... the fetch also counts as a clone. Even actions/checkout registers a clone. Back to using the API for as much as possible.