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Description
Right now, the way we determine the code forge is by matching the remote URL.
For GitHub, it must be github.com, or whatever is configured with GITHUB_URL.
Per discussion in #330, a better UX for GHES would be the ability to specify that they're using a specific kind of forge (e.g. GHES), and then the GitHub URL is determined based on the Git remote, and the API URL guessed based on that.