- change the messaging depending on how confident we are that we're
actually looking at duplicates i.e. we're not confident without a
version number supplied
- similarly, just warn instead of failing with an error (and no
override) if we're not confident that we're looking at duplicates
because a version wasn't supplied
- change `bump-cask-pr` and `bump-formula-pr` to always check for all
pull requests with the new version number (to allow failing on this)
rather than only checking closed pull requests with a version number
- change `bump` to check for definite/maybe duplicate PRs and only
exit if they are definitely duplicates
- cleanup some variable usage to DRY things up a bit
fe909c41b8