Use `gh repo set-default` information?

[nedbat]

The GitHub gh tool has a command gh repo set-default that sets a default remote when there is more than one. We could use this to determine which remote to use for scriv github-release.

When you use gh repo set-default nedbat/something, a setting is put into the .git/config file:

[remote "origin"]
        url = [email protected]:nedbat/something.git
        fetch = +refs/heads/*:refs/remotes/origin/*
        gh-resolved = base     # <--- new setting