Squashing a merge request should leave a system note
Description
When a merge request has been merged with a squash option, there is no indication of this fact in the user interface.
Without a system note / something else it is very difficult to know when a merge request has been squashed before merge.
I sometimes browse commits history / use my Git-fu when I see that git branch --merged does not show my branch, even when I'm sure a merge request has been merged already.