>>Yes, it's not 100% automatable without a bit of per-tool scripting. The workload is minimal compared to writing the tools. Perhaps in an ideal world it could be completely automated, but that just shifts the burden from writing the autocompletion code to writing some sort of reflective description of the system. Big deal.
>And in PowerShell I get autocompletion basically for free. And it's good. It's VERY good. I'm actually using PowerShell instead of Postgres's psql because PowerShell is much more powerful.
You only get this for free, if your software is designed to work with PowerShell, otherwise you are in the same boat as with zsh/bash.
There is at least one framework (twisted-python) that automatically generates zsh completions from the description of options.