Show dependencies in pipeline graph
Description
Currently (and please correct me if I'm wrong), the "pipeline graph" is no real graph, but rather a set (if more than 1 stage) of lists (jobs per stage) that have lines to make it look a bit more pretty. The lines actually don't have any meaning (apart from maybe indicating that stuff is happening in parallel in the sequentially run stages).
Proposal
Use the lines in the "graph" in a more sensible way and show possible dependencies as expressed by the .gitlab-ci.yml
.