Let users configure dist mode in the configuration file

[nicoddemus]

Fix #789

[RonnyPfannschmidt]

we ought o consider having a ini option for the default dist mode which is cleaner than addopts (similar to the logging plugin

[nicoddemus]

Thanks @RonnyPfannschmidt for the review.

we ought o consider having a ini option for the default dist mode which is cleaner than addopts (similar to the logging plugin

I was writing my rationale why I think it is not necessary and it turned out to be quite verbose, so I decided instead to turn that into an issue in pytest so we can bring more people to the discussion. 👍

Please read my rationale there, and if you still feel strongly we should have a dedicated option for it, I will be glad to do it in a follow-up (because another small option would not really be the end of the world). It is also arguable that --dist should have been a configuration option in the first place.

I think this is worthwhile to merge anyway as it provides a fix for the original issue and cleans up the code a bit, removing what seemed to be a wart that --dist without -n would give a cryptic message like that.