adapt plugin printing

[RonnyPfannschmidt]

• print each distribution only once(xdist now has 3 entrypoints)
• include the distribution version

[pfctdayelise]

OK so I just pip-installed xdist, I guess I don't have the version that would cause duplication on master. But having plugin version info definitely seems like a good idea.

Master:

platform linux2 -- Python 2.7.6, pytest-2.8.0.dev4, py-1.4.30, pluggy-0.3.0
rootdir: /home/brianna/workspace/pytest, inifile: tox.ini
plugins: xdist

this branch:

platform linux2 -- Python 2.7.6, pytest-2.8.0.dev4, py-1.4.30, pluggy-0.3.0
rootdir: /home/brianna/workspace/pytest, inifile: tox.ini
plugins: xdist 1.12

[pfctdayelise]

I imagine it's a pain to install a plugin in a test, but could we make a test? Or do you think because this gets exercised so much it's not worth it.

[pfctdayelise]

It would be nice if this was joined by a dash rather than space, for consistency with the builtin plugins on line 281.

getpluginversioninfo suggests you can do dist.project_name, dist.version

[RonnyPfannschmidt]

good idea, thanks

[RonnyPfannschmidt]

will reopen from a branch, made it from master by accident (thanks git)