MR with fork can mess up upstream project's issues
Created by: roboogle
Summary
Accepting MR involving forked project, may wrongly close issues in upstream project.
Steps to reproduce
Suppose you have project P1 and fork a project P2 out of P1: P1 is upstream, P2 is fork.
Now you work on P2, and fix issue #1 with a commit C1 whose message contains Fixes #1.
Then open a MR of P2 into P1, containing commit C1.
Accepting the MR, will correctly close P2#1, but will also close P1#1 which is wrong as it may be a completely unrelated issue.
Expected behaviour
Wrt the previous example, when accepting MR, issue P2#1 shall be closed, and issue P1#1 shall be not closed.