Random comment about a thing that's been mildly bothering me for a while:
If you were wondering why scp remote tab-completion stopped working recently (-ish) in ZSH when the remote is a Kindle, it's because of
this ZSH fix, which breaks on Kindle, because the Kindle's busybox build doesn't ship the 'command' applet (that's stupid).
Not really fixable on the Kindle side, as that's a shell builtin, not a standalone command.
ZSH is entirely right in expecting command to exist, because This Is The Way to do this right (as per POSIX).