Improvements for Multi-Project Pipeline Mini-graph

In #2602 (closed) we've mini-graph for multi-project pipelines in the MR widget.

  1. It looks good if you've multiple downstreams, but with a single one it probably has less space than needed on the right margin. You can see in the image the distance between the green circle and the "for" word. mini-graph

  2. There is an extra line from the last stage in the main pipeline in direction of the connecting arrow (this affects also multi-downstream cases).

Edited by Fabio Busatto