Branch-name-conventions missing

#### Describe the bug
The chapters in the official documentation
- 4.3.7. Branching workflow for member contributors
- 4.3.8. Forking for non-member contributors 
both state:
> Create a branch with a meaningful name. Follow the branch-name conventions.

But there are no *branch-name conventions* at all.

What are the branch-name conventions? Where do we put it? In 4.3.7. I guess?