feat: add autocompletion support

[mchlumsky]

Fixes #637

[max-wittig]

Thanks for this feature. Doesn't work for me with the provided instructions and zsh.

[mchlumsky]

Hi!

Indeed it doesn't work. I thought it was just my setup that didn't work. I don't really use zsh so my testing of it was light. The other shells do work though. I use this patch in bash all the time with no problems at all.

Argcomplete sounded like a quick win. It's used by pipx 1 and others.
It doesn't sound like the author of argcomplete cares much about zsh 2.

Should I remove any mention of zsh from the docs? Or should we mention zsh support as experiemental/broken with a reference to the issue 2?
Or is this a show stopper?

[max-wittig]

@mchlumsky I guess we should add a notice that it doesn't work with zsh.

Can we make argcomplete optional somehow? I think most people don't use the CLI.

[mchlumsky]

I kept the commits separate for clarity but I can squash them into one once they pass peer-review.

[max-wittig]

@mchlumsky Looks good to me now! Could you just squash those commits and then we can merge it 😃

[mchlumsky]

Commits squashed! However travis-ci testing is failing during some rate-limit testing in py_func_v4.
I tried rebasing against latest master but I still get the failure.
I don't think the failure is related to this merge request.

[max-wittig]

@mchlumsky Sadly the build pipeline is not as stable as I want it to be. But I can't figure out why as everything works fine locally, everytime.

[mchlumsky]

@max-wittig The test that failed in my run was this one. It's a rate limit test, which can be almost described as a performance test. The test fails because it can't trigger the rate limiting feature of gitlab. This kind of test is hard to achieve on a public shared service like travis-ci where the VMs running your tests can have very different sizes and/or workloads.
I am pretty impressed with the functional testing you've achieved (spinning up a gitlab instance and testing against it). I didn't know you could pull that off with travis-ci! Kudos for that! ;)

[max-wittig]

@mchlumsky Thank you, but credit goes to the original creator of this lib, not to me. @gpocentek

[max-wittig]

But I guess we should remove this test.