chore: Refactor types for fetching GitHub content

[kemmerle]

Description and Context

Is a dependency of: HubSpot/hubspot-cli#1288

As part of our work to convert the CLI to TypeScript, we're typing prompts that rely on downloading content from GitHub. We were mistakenly returning the Buffer type from the fetchFileFromRepository function. In fact, this function returns the contents of the file (resp.data) we're downloading. Since literally anything can be in a file downloaded from GitHub, this is an instance of a true any type, in my opinion.

TODO

• Address feedback.

Who to Notify

@camden11 @brandenrodgers @joe-yeager

[camden11]

Hmm I can see how Buffer is causing some issues but I think we could come up with a more type safe approach here. First, Buffer is technically correct since we're fetching a file from the endpoint, but it seems like when you fetch a json file, Axios knows how to handle it and treats it like a normal endpoint response. I think the move here is probably to use a generic type so we can tell the fetchFileFromRepository what to expect if we know it's not a Buffer. We should also extend this to the fetchRepoFile function in api/github

export function fetchRepoFile<T = Buffer>(
  repoPath: RepoPath,
  filePath: string,
  ref: string
): HubSpotPromise<T> {
  return axios.get<T>(
    `${GITHUB_RAW_CONTENT_API_PATH}/${repoPath}/${ref}/${filePath}`,
    {
      headers: {
        ...getDefaultUserAgentHeader(),
        ...getAdditionalHeaders(),
      },
    }
  );
}

and then you can add the generic type to fetchFileFromRepository as well