display a short documentation with the -l/ show envlist (a concatenation of the environments description)

[gaborbernat]

This is the implementation for #462.

For example:

[tox]
envlist={py27,py36}-{windows,linux}
[testenv]
description= py27: run py.test on Python 2.7
             py36: run py.test on Python 3.6
             windows: on Windows platform
             linux: on Linux platform
             docs: generate documentation
commands=py.test {posargs}

[testenv:docs]
changedir = docs

tox -l 
py27-windows run py.test on Python 2.7 on Windows platform
py27-linux   run py.test on Python 2.7 on Linux platform
py36-windows run py.test on Python 3.6 on Windows platform
py36-linux   run py.test on Python 3.6 on Linux platform

[The-Compiler]

This should be {0} {1} to work on Python 2.6 - it seems like it doesn't get caught in the tests though, and they report "can not run tests involving calling tox on python2.6. (and python2.6 is about to be deprecated anyway)"...

[gaborbernat]

@The-Compiler indeed, fixed that, thanks!

[gaborbernat]

@The-Compiler , @obestwalter now that the CI checks passed, can you guys take a look? thanks!

[The-Compiler]

LGTM (though I don't know tox' code very well), but I'll let @obestwalter press the button 😉

[nicoddemus]

LGTM as well, but I feel we should add docs about this new feature first.

[obestwalter]

ha - nice to see it's being used already - does not really belong to this PR, but won't hurt anyone to just add it now, I guess :)

[obestwalter]

@The-Compiler what an honour :D - I agree with @nicoddemus that this deserves some documentation (somewhere here-ish) before we call this done.

[gaborbernat]

@obestwalter hmm, I thought that's automatically taken during documentation generation from here:

 parser.add_testenv_attribute(
        name="description", type="string", default='', postprocess=merge_description,
        help="short description of this environment")

Where is that shown otherwise?

[The-Compiler]

When doing tox --help

[gaborbernat]

@obestwalter , @The-Compiler done 👍

[obestwalter]

Played around with it locally a bit and it looks good. Looking forward to the next step that fixes #271.

[The-Compiler]

I can't get this to work with the 2.7.0 preview with this tox.ini. Both description = Hello World in [testenv:py36-cov] (which is what I'd expect to work by reading the docs) and description = py36-cov: Hello World in [testenv] (which seems odd, but what the tests do) still gives me no description in the env list.

[obestwalter]

o.k. just tried the unconditional approach with 2.7.0 from devpi with this ini:

[tox]
envlist={py27,py36}-{windows,linux}
[testenv]
description= hello world

[testenv:docs]
description = blablabla


$ tox -l

py27-windows hello world
py27-linux   hello world
py36-windows hello world
py36-linux   hello world

$ tox -l -e docs

docs blablabla

So from how I understand it, it works like it should. Am I missing something?

[The-Compiler]

Oh, damn, my bad! I was running my systemwide tox instead of the one from the virtualenv... nevermind! 😊

[gaborbernat]

@obestwalter cool, submitted the PR for #271 in #495