Add initial workflow rules
This adds an initial workflow:rules
section that prevents duplicate pipelines in certain edge cases. This is already prevented by the individual job rules, but jobs imported in includes:
sections could still cause this problem, so we should lock it down pipeline-wide.
This came up as part of the discussion in gitlab-org/frontend/untamper-my-lockfile!12 (comment 503081636).
- Related to gitlab#299409 (closed)
Edited by Marcel Amirault