add checks and properties to see if uri is from github

Author: Jasmine

src/GitHub.Exports/Primitives/UriString.cs

@@ -77,6 +77,7 @@ void SetUri(Uri uri)
             }
 
             IsHypertextTransferProtocol = uri.IsHypertextTransferProtocol();
+            IsGithubUri = uri.IsGithubUri();
         }
 
         void SetFilePath(Uri uri)

src/GitHub.Extensions/UriExtensions.cs

@@ -25,6 +25,11 @@ public static bool IsHypertextTransferProtocol(this Uri uri)
             return uri.Scheme == "http" || uri.Scheme == "https";
         }
 
+        public static bool IsGithubUri(this Uri uri)
+        {
+            return uri.OriginalString.Contains("github.com");
+        }
+
         public static bool IsSameHost(this Uri uri, Uri compareUri)
         {
             return uri.Host.Equals(compareUri.Host, StringComparison.OrdinalIgnoreCase);

src/GitHub.VisualStudio/Base/MenuBase.cs

@@ -44,7 +44,8 @@ void RefreshRepo()
         protected bool IsGitHubRepo()
         {
             RefreshRepo();
-            return ActiveRepo?.CloneUrl?.RepositoryName != null;
+            return ActiveRepo?.CloneUrl?.RepositoryName != null && ActiveRepo?.CloneUrl?.IsGithubUri == true;
+
         }
     }
 }