Allow docker test rake task to be used for single plugins #4973
This is useful for adding continuous integration to individual plugin repositories. For example, I've just set up discourse-chat-integration to run its tests on travis automatically. (Currently it applies this patch manually).
This change adds support for a
(Specific qunit tests can already be run using the
Where would you like the documentation? As a comment at the top of the file? I think a list of all the possible environment variables is probably a bit long to fit in the description line