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Based on discussion in #502 (comment), I thought we did retry on a sync fork failure, but after looking at the code again, it appears we don't. This change makes it so that we attempt to sync fork multiple times if the first attempt fails for any reason. Doing this as it appears users are running into this issue even with the changes made in #581 (but can't confirm if they are in fact using the latest version). I think it's generally better if we attempt retries on sync fork step.

Validation

Validated manually by setting response to have a 422 status code (to throw a GenericSyncForkException) in UpdateForkedRepoWithUpstreamCommits function as

//var response = await httpClient.PostAsync(url, content);
var response = new HttpResponseMessage
{
    StatusCode = System.Net.HttpStatusCode.UnprocessableEntity
};

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