See

• https://github.com/tqdm/shtab/releases/tag/v1.9.0
• https://fishshell.com/docs/current/completions.html#where-to-put-completions

FISH completions previously had to be generated from parsing the man page. Users had to do this manually. With shtab adding support for FISH, we can finally build them here and include them in the sdist and bdist files, like the other shell completion files.

I've tested the new completions and they work fine. Better than the man-page-generated ones, as argument value choices are supported now (e.g. --loglevel=).

This PR also rewrites the build script in Python, as it's much cleaner and extensible this way.

Since we've bumped our shtab dependency to >=1.9.0 for being able to also build completions for FISH, in environments where this version of shtab is not available (yet), shells have to set explicitly as args on the build script: ./script/build-shell-completions.py bash zsh