I didn't initially use GitHubRepo because it had the weird error
wrapping. I poked around and I think this function is leftover from a
vestigial GitHubRepoID function that used to be more single-purpose. I
took out the weird error handling so it could be reused and then used it
from the new GitHubRepoExists.
```
$ gh repo
Work with GitHub repositories.
A repository can be supplied as an argument in any of the following formats:
- by owner/repo, e.g. "cli/cli"
- by URL, e.g. "https://github.com/cli/cli"
Usage:
gh repo [command]
Available Commands:
view View a repository in the browser
```
