Rather than connecting directly to the GitHub API I opted to mock out the data structures to simulate those that I would probably create subsequent to data retrieval.
In a realistic scenario the data required to find the shortest path would need to be lazily loaded from the API, cached, the search depth limited and more error handling introduced. For the purposes of this demo that functionality does not exist.
The container app is a Spring Boot app, dependency managed and built using Maven, tests in JUnit, and running on Java 9.
To run the demo via the tests use mvn test.
The following files contain comments outlining my thoughts as I was building this demo:
Apologies in advance for the quality of the Java, it has been a few years since I've written any and there should probably be more JavaDoc.