This is how it must be:
The ./ tells GitHub to begin in the home directory of the repository. then you can add a / and after that the folder name and name of the image like the example i gave.
Although it might not be specifically helpful on on logic operators AND and OR, this GitHub guide links to many extremely helpful areas, a quick scan of the list may be useful (I was trying to find how to limit my search by language, and found it in about 15 seconds).
Also, this Guide to GitHub Search Syntax does cover the NOT operator (which is a start, at ...