Some remarks:
- Because of github API limits (especially on pull requests endpoint) too many search and/or pull to refresh actions can cause "Forbidden" responses.
- I wanted to avoid N+1 queries so there's no first and lastname of an user on search screen.
- GitHub does not provide information about open and total pull requests for repository (or at least I haven't found such one). Because of that and because of incremental loading there's no gray bar with open/total pull requests on pull requests view.
- There's no description field for pull request in API - I considered using description of head comment but I resigned - this field is markdown, which requires additional libraries to convert to html and put as web control on PR cell and I had no time to do so.
- Some classes (especially ViewModels) can be refactored (e.g. base classes can be introduced to reduce code duplication) - not done because of lack of time.
- Also because of lack of time I have not implemented Unit/UI Tests.