If the `rebuild`, `root_url`, `cellar` and checksums are all identical
between an old and new bottle block: we don't need a new bottle at
all. Handle this by deleting the relevant files with
`brew bottle --merge --write` and gracefully notifying the caller of
`brew pr-upload`.
This should avoid e.g.
https://github.com/Homebrew/homebrew-core/commit/39340a11eaa9a380616e63d96eb813731b9f00e8
occurring in future.
Mike McQuaid
d44d686cd5