This was failing for me locally so I've made some fixes:
- remove the `markdown` flag (as it's the only path now)
- refactor the generation to not use intermediate variables
- discard more weird cases rather than erroring
- exclude @Homebrew changes (e.g. from bots) because we don't care about
these in the release notes
Some merge commits don't include the title of the pull request
on subsequent lines, leaving the markdown link text blank
in the release notes. This appends the subject line of the
commit message instead if the body is missing and adds a test
case.
