Include usage example in CLI help command output

Author: nblumhardt

src/SeqCli/Cli/Commands/App/UpdateCommand.cs

@@ -81,6 +81,12 @@ protected override async Task<int> Run()
             return 1;
         }
 
+        if (_all && _version != null)
+        {
+            Log.Error("The `all` and `version` options are incompatible");
+            return 1;
+        }
+        
         if (!_all && _id == null && _name == null)
         {
             Log.Error("One of `id`, `name`, or `all` must be specified");

src/SeqCli/Cli/Commands/HelpCommand.cs

@@ -63,8 +63,17 @@ protected override Task<int> Run(string[] unrecognized)
                     var subCommandHelp = subCommand == null ? "" : " " + subCommand;
                     Console.WriteLine(name + " " + cmd.Metadata.Name + subCommandHelp + argHelp);
                     Console.WriteLine();
+
                     Console.WriteLine(cmd.Metadata.HelpText);
                     Console.WriteLine();
+
+                    if (cmd.Metadata.Example != null)
+                    {
+                        Console.WriteLine("Example:");
+                        Console.WriteLine($"  {cmd.Metadata.Example}");
+                        Console.WriteLine();
+                    }
+                    
                     cmd.Value.Value.PrintUsage();
                     return Task.FromResult(0);
                 }