Merge branch 'master' into 'master'

"Fixes #xxxx" now shows up in the issue log for non-default branches. #2190

I don't understand why the commits containing "closing references" (like `closes #xxxx`) were not mentioned in the corresponding issues **when pushed to a non-default branch**.

So I tried to discover how it works -- hence learning Ruby! I don't expect that MR to pass, this is my very first attempt of contribution.

**Update:** my modifications are now done. To sum up:
- when a commit with a reference `fixes #xxxx` is pushed to a non-default branch, a cross-reference to that issue will be created;
- when that same commit is pushed to a default branch, no cross-reference will be created because a message `This commit closes issue` will be emitted.
- I also refined some of the existing tests and added 2 tests on the new behavior on non-default branches.

See merge request !1150