regression: add Jenkinsfile

[jfontan]

Only runs on master branch and it checks SCM twice a day. Uses the queries from _testdata/regression.yml.

[erizocosmico]

Being this so tied with our cluster config, should this be here in the public repo?

[jfontan]

We use a type of Jenkins job that discovers Jenkinsfile in repositories and runs whatever they have in. This lets us configure Jenkins once and add these files to repositories to enable these type of tests. AFAIK there is no way of merging parts hardcoded with the steps specific to projects, for example taking out the kubernetes part from this file.

We can go the other way and create Jenkins jobs per repository but this becomes tedious as any change to the Jenkinsfile or adding new repositories means changing Jenkins deploy recipes and deploying it again.

If this file seems out of place we can change its name or move it to another directory, for example .srcd-ci/Jenkinsfile.

[smola]

AFAIK there is no way of merging parts hardcoded with the steps specific to projects, for example taking out the kubernetes part from this file.

As discussed offline, there is nothing here that we need to keep secret. Other than that, we'll eventually refactor these Jenkinsfile to use a shared library, to reduce boilerplate.