Special case single star branch/tag constraint

[michaelsauter]

If the constraint is e.g. branches: ["*"], then all branch names are matched, even ones containing slashes. Before this change, e.g. feature/foo would not have matched.

Closes #691.

Tasks:

• [x] Updated design documents in docs/design directory or not applicable
• [x] Updated user-facing documentation in docs directory or not applicable
• [x] Ran tests (e.g. make test) or not applicable
• [x] Updated changelog or not applicable

[henninggross]

I believe the docs of the configuration need to be updated as well. I am on my phone sadly and cannot link to the specific lines, but there is a place where it is mentioned that "*" does not catch every branch.