RFC: Add docker compose file for running non-native test environments

[toofar]

Would anyone else find it useful to be able to spin up the same containers that are used in CI? Is docker-compose a goood interface for doing so?

Opinions welcome!

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I find it difficult to reproduce issues on old python versions, or when archlinux brings in a newer build of Qt than I have and I can't be bothered rebuilding.

I've been using docker for a while to help test in these environments locally, but the docker command is a bit long and unwieldy. Docker compose is a method I've used before to provide canned docker invocation. We could probably get away with writing our own script for it, but using standard components is good. This should work with podman-compose too.

This commit encodes the docker command I've been using so that I, and other people, can use it with a less arcane command line. Hopefully it helps other people. There are still a few rough edges like for any runs of the "other" service you will pretty much have to drop into a bash shell and install tox and some X11 stuff. But the images we publish work in one-liners (although they would be a little faster with a tox/pip cache directory mounted from the host so they don't setup the venv every time).

See also: the docker related hints in the contributor guidlines.

[The-Compiler]

The file should probably live somewhere in misc/ or so? Also to make it clear that this is not something intended for users of qutebrowser.

Docker compose seems like a fitting tool if your goal is to basically persist Docker commandlines. I use it too for various things like that. However, see below.

I wonder if act wouldn't be a better fit for this? It looks like e.g. act -j tests-docker --matrix image:archlinux-webengine-unstable-qt6 can run the tests in that environment without any additional effort (and duplication!). But I suppose your goal here is also local debugging (having a shell, X11 passthrough, etc.), so I suppose that approach is a tad too simple in the end?