Deletes old formulas from Homebrew.
Homebrew is a package manager for macOS. It's documentation says:
"By default, Homebrew does not uninstall old versions of a formula, so over time you will accumulate old versions. To remove them, simply use:
This is a strategy that can easily save gigabytes of data, as you can see in this Twitter thread:
$ brew cleanup— Max Stoiber (@mxstbr) 16. Mai 2018
> ==> This operation has freed approximately 1.2GB of disk space.