- There's a TODO on the "someday" list [1] to ensure that `head` Git
URLs always specify a branch.
- So I thought I'd automate this worry by adding an audit.
- Since `resource` block URLs tend to be pinned to SHAs, if indeed
they are Git URLs, this audit only applies to `head` URLs.
[1]: https://github.com/orgs/Homebrew/projects/5?pane=issue&itemId=98789749