Return types do not indicate nullability

[winstliu]

Many methods can return null, but the API surface does not reflect this.

For example, GitApi.getRepositories(project) returns null if the project doesn't exist, but the return type is misleadingly listed as Promise<GitRepository[]>.

[aleksandrlevochkin]

Hi @winstliu thank you for reporting this issue. We are currently working on higher-prioritized issues, but we'll return to this one as soon as we can