issue id's should be unique to prevent accidently closing when merging between projects

If you merge one project into an other project, the issues of the one project gets automaticaly closed because of the commit messages in the other merged project.

We often use one project for the product (= master project), and fork that project for customers who wants modifications.

When there's a bug in the main project, we fix it and close the issue with a commit message (ie. fix #1: Become a programmer, they said. It'll be fun, they said.)
The customers project also got an issue #1, but is totaly unreleated to the master project issue #1.
When you merge the master project into customers project, the customers issue #1 gets also closed because of the merged commit fix #1: Become a programmer, they said. It'll be fun, they said..

This unwanted behavior can be avoided if all issues would have an unique id, like it used to be in Gitlab. So there can be only one #1.