Work around GitHub API has_wiki defect

Author: HebaruSan

Netkan/Sources/Github/GithubApi.cs

@@ -50,7 +50,7 @@ public GithubApi(IHttpService http, string? oauthToken = null)
 
         public GithubRepo? GetRepo(GithubRef reference)
             => Call($"repos/{reference.Repository}") is string s
-                   ? JsonConvert.DeserializeObject<GithubRepo>(s)
+                   ? CheckForWiki(reference, JsonConvert.DeserializeObject<GithubRepo>(s))
                    : null;
 
         public GithubRelease? GetLatestRelease(GithubRef reference, bool? usePrerelease)
@@ -98,6 +98,19 @@ public List<GithubUser> getOrgMembers(GithubUser organization)
                     : null)
                ?? new List<GithubUser>();
 
+        private GithubRepo? CheckForWiki(GithubRef reference, GithubRepo? repo)
+        {
+            if (repo is { HasWiki: true })
+            {
+                repo.HasWiki = ActuallyHasWiki(reference);
+            }
+            return repo;
+        }
+
+        private bool ActuallyHasWiki(GithubRef reference)
+            // If no wiki pages have been created, the /wiki route redirects and this is null
+            => _http.DownloadText(new Uri($"https://github.com/{reference.Account}/{reference.Project}/wiki")) != null;
+
         /// <summary>
         /// Download a URL via the GitHubAPI.
         /// Will use a token if we have one.