.travis.dist.yml: Use Travis build stages when configuring your build

[Dagefoerde]

Thanks again for having merged the --no-init option in #66. We have been successfully able to leverage it to use build stages in our projects (https://travis-ci.org/learnweb/moodle-repository_owncloud/builds/334743893, https://travis-ci.org/learnweb/moodle-mod_collaborativefolders/builds/328301352) and it's very useful.

Here's how the .travis.yml needs to be configured to make use of that option in combination with build stages.

[danmarsden]

just tried this out - thanks for the pointers! - FYI - I found that it didn't seem to respect the env/global settings and needed each db/moodle version to be specific in the matrix eg:
https://github.com/catalyst/moodle-tool_coursebank/blob/master/.travis.yml#L24

[Dagefoerde]

Wasn't it respected at all? IIRC, if you specify variables in env/global it will be added to every element in the matrix. But it does not construct full matrices by building a cross product from different variable values, so in your case you have to specify every combination explicitly, correct. We usually do that in our plugins just like you did (https://github.com/learnweb/moodle-repository_owncloud/blob/2c0966ccde558df5e7aa9d79c5905c523e93d3de/.travis.yml#L24-L29).