They just pack a statically compiled Ruby interpreter with Homebrew. Not very complex or novel. Disadvantage: install becomes more bloated (larger size).
Sure, it’s not a hard engineering challenge. However, installation instructions right now are as simple as “run this one-liner on your terminal”. That’ll have to materially change.
> Sure, it’s not a hard engineering challenge. However, installation instructions right now are as simple as “run this one-liner on your terminal”. That’ll have to materially change.
It could just as well still remain a one-liner. Every system Homebrew is installed on has Bash installed (not the latest, but still).
> Every system Homebrew is installed on has Bash installed
Ironically, they are also moving from bash to zsh for default shell. Again not an unsurmontable challenge (just make sure the bang is correct in your scripts, bash will likely still be around somewhere in macOS for the foreseeable future) but another little hurdle to mind.
As far as I'm aware they're not changing anything about which shells are installed or which executable /bin/sh points to they're just changing the default login shell for a new user, so nothing should have to change about the scripts that are (or have been) written.