Split the two command implementations into separate libraries (#2012)

This will allow us at the user code side to determine to include old commands, new commands or both.

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

@@ -0,0 +1,92 @@
+/*----------------------------------------------------------------------------*/
+/* Copyright (c) 2019 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.                                                               */
+/*----------------------------------------------------------------------------*/
+
+#pragma once
+
+#include <iostream>
+#include <memory>
+#include <utility>
+
+#include "CommandBase.h"
+#include "CommandGroupBase.h"
+#include "CommandHelper.h"
+
+namespace frc2 {
+/**
+ * Runs one of two commands, depending on the value of the given condition when
+ * this command is initialized.  Does not actually schedule the selected command
+ * - rather, the command is run through this command; this ensures that the
+ * command will behave as expected if used as part of a CommandGroup.  Requires
+ * the requirements of both commands, again to ensure proper functioning when
+ * used in a CommandGroup.  If this is undesired, consider using
+ * ScheduleCommand.
+ *
+ * <p>As this command contains multiple component commands within it, it is
+ * technically a command group; the command instances that are passed to it
+ * cannot be added to any other groups, or scheduled individually.
+ *
+ * <p>As a rule, CommandGroups require the union of the requirements of their
+ * component commands.
+ *
+ * @see ScheduleCommand
+ */
+class ConditionalCommand
+    : public CommandHelper<CommandBase, ConditionalCommand> {
+ public:
+  /**
+   * Creates a new ConditionalCommand.
+   *
+   * @param onTrue    the command to run if the condition is true
+   * @param onFalse   the command to run if the condition is false
+   * @param condition the condition to determine which command to run
+   */
+  template <class T1, class T2,
+            typename = std::enable_if_t<
+                std::is_base_of_v<Command, std::remove_reference_t<T1>>>,
+            typename = std::enable_if_t<
+                std::is_base_of_v<Command, std::remove_reference_t<T2>>>>
+  ConditionalCommand(T1&& onTrue, T2&& onFalse, std::function<bool()> condition)
+      : ConditionalCommand(std::make_unique<std::remove_reference_t<T1>>(
+                               std::forward<T1>(onTrue)),
+                           std::make_unique<std::remove_reference_t<T2>>(
+                               std::forward<T2>(onFalse)),
+                           condition) {}
+
+  /**
+   * Creates a new ConditionalCommand.
+   *
+   * @param onTrue    the command to run if the condition is true
+   * @param onFalse   the command to run if the condition is false
+   * @param condition the condition to determine which command to run
+   */
+  ConditionalCommand(std::unique_ptr<Command>&& onTrue,
+                     std::unique_ptr<Command>&& onFalse,
+                     std::function<bool()> condition);
+
+  ConditionalCommand(ConditionalCommand&& other) = default;
+
+  // No copy constructors for command groups
+  ConditionalCommand(const ConditionalCommand& other) = delete;
+
+  void Initialize() override;
+
+  void Execute() override;
+
+  void End(bool interrupted) override;
+
+  bool IsFinished() override;
+
+  bool RunsWhenDisabled() const override;
+
+ private:
+  std::unique_ptr<Command> m_onTrue;
+  std::unique_ptr<Command> m_onFalse;
+  std::function<bool()> m_condition;
+  Command* m_selectedCommand{nullptr};
+  bool m_runsWhenDisabled = true;
+};
+}  // namespace frc2