Addition of parallel runs and dependencies is awesome, but we quite miss any support for factors or glob patterns in the depends option.

In case we have several environments

[tox]
envlist = clean-coverage,py27,py35,py36,py37,compute-coverage

we have to set dependencies for compute-coverage individually

[testenv:compute-coverage]
depends = py27,py35,py36,py37

which is error prone and not quite comfortable.

I suggest to allow glob patterns

[testenv:compute-coverage]
depends = py*

and factors similarly to other parts of configuration.

I don't quite feel I would be able to provide a PR.