Add ArrayRef overloads to new command classes (#2216)

Also default requirements to {} in all cases for consistency.

wpilibNewCommands/src/main/native/include/frc2/command/InstantCommand.h

@@ -1,5 +1,5 @@
 /*----------------------------------------------------------------------------*/
-/* Copyright (c) 2019 FIRST. All Rights Reserved.                             */
+/* Copyright (c) 2019-2020 FIRST. All Rights Reserved.                        */
 /* Open Source Software - may be modified and shared by FRC teams. The code   */
 /* must be accompanied by the FIRST BSD license file in the root directory of */
 /* the project.                                                               */
@@ -10,6 +10,8 @@
 #include <functional>
 #include <initializer_list>
 
+#include <wpi/ArrayRef.h>
+
 #include "frc2/command/CommandBase.h"
 #include "frc2/command/CommandHelper.h"
 
@@ -29,7 +31,17 @@ class InstantCommand : public CommandHelper<CommandBase, InstantCommand> {
    * @param requirements the subsystems required by this command
    */
   InstantCommand(std::function<void()> toRun,
-                 std::initializer_list<Subsystem*> requirements = {});
+                 std::initializer_list<Subsystem*> requirements);
+
+  /**
+   * Creates a new InstantCommand that runs the given Runnable with the given
+   * requirements.
+   *
+   * @param toRun        the Runnable to run
+   * @param requirements the subsystems required by this command
+   */
+  InstantCommand(std::function<void()> toRun,
+                 wpi::ArrayRef<Subsystem*> requirements = {});
 
   InstantCommand(InstantCommand&& other) = default;