Visual update for merge requests
Created by: riyad
This is a try to update how merge requests are displayed with regard to consistency and feature interoperability.
It changes the following things:
- use GFM style notation for MR ids (i.e. "Merge Request !123" instead of "Merge Request #123")
- make GFM ids more prominent (especially on the index page)
- make it clearer that the avatar image is associated with the author not with the MR (on the index page)
- make the author a link (on the index page as it already is on the show page)
- the source and target branch displays look the same on the index and show pages