Apply suggestions from code review

Co-authored-by: Matthew John Cheetham <[email protected]>

Author: hickford

src/shared/GitHub/GitHubAuthentication.cs

@@ -76,16 +76,12 @@ public async Task<AuthenticationPromptResult> GetAuthenticationAsync(Uri targetU
                 throw new ArgumentException(@$"Must specify at least one {nameof(AuthenticationModes)}", nameof(modes));
             }
 
-            switch (modes)
+            // If there is no mode choice to be made and no interaction required,
+            // just return that result.
+            if (modes == AuthenticationModes.Browser ||
+                modes == AuthenticationModes.Device)
             {
-                case AuthenticationModes.Browser:
-                    // no user interaction required
-                    return new AuthenticationPromptResult(AuthenticationModes.Browser);
-                case AuthenticationModes.Device:
-                    // no user interaction required
-                    return new AuthenticationPromptResult(AuthenticationModes.Device);
-                default:
-                    break;
+                    return new AuthenticationPromptResult(modes);
             }
 
             ThrowIfUserInteractionDisabled();

src/shared/GitHub/GitHubHostProvider.cs

@@ -316,10 +316,7 @@ public static bool IsGitHubDotCom(string targetUrl)
 
         public static bool IsGitHubDotCom(Uri targetUri)
         {
-            if (targetUri is null)
-            {
-                throw new ArgumentNullException(nameof(targetUri));
-            }
+            EnsureArgument.AbsoluteUri(targetUri, nameof(targetUri));
 
             return StringComparer.OrdinalIgnoreCase.Equals(targetUri.Host, GitHubConstants.GitHubBaseUrlHost);
         }