I think the real problem is that other apps do use ssh and malicious actors can inject untrusted input without the user's consent.
The git POC is one example, and while I do think that git also needs to be updated, fixing the problem on the ssh side is also a good idea
It needs to be changed to pass data in a way that doesn't require escaping to reference, such as an environment variable: "$HOST" would then be expanded by the shell, and all the usual rules for safely using environment variables would apply, because ssh wouldn't be the thing performing the variable expansion like it is now.
(For most purposes, my original take in the top level was wrong, but it's too late to edit it now)
A good discussion on this: https://gist.github.com/egmontkob/eb114294efbcd5adb1944c9f3c...