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/cpp/frc2/command/ConditionalCommand.cpp

@@ -0,0 +1,52 @@
+/*----------------------------------------------------------------------------*/
+/* 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.                                                               */
+/*----------------------------------------------------------------------------*/
+
+#include "frc2/command/ConditionalCommand.h"
+
+using namespace frc2;
+
+ConditionalCommand::ConditionalCommand(std::unique_ptr<Command>&& onTrue,
+                                       std::unique_ptr<Command>&& onFalse,
+                                       std::function<bool()> condition)
+    : m_condition{std::move(condition)} {
+  if (!CommandGroupBase::RequireUngrouped({onTrue.get(), onFalse.get()})) {
+    return;
+  }
+
+  m_onTrue = std::move(onTrue);
+  m_onFalse = std::move(onFalse);
+
+  m_onTrue->SetGrouped(true);
+  m_onFalse->SetGrouped(true);
+
+  m_runsWhenDisabled &= m_onTrue->RunsWhenDisabled();
+  m_runsWhenDisabled &= m_onFalse->RunsWhenDisabled();
+
+  AddRequirements(m_onTrue->GetRequirements());
+  AddRequirements(m_onFalse->GetRequirements());
+}
+
+void ConditionalCommand::Initialize() {
+  if (m_condition()) {
+    m_selectedCommand = m_onTrue.get();
+  } else {
+    m_selectedCommand = m_onFalse.get();
+  }
+  m_selectedCommand->Initialize();
+}
+
+void ConditionalCommand::Execute() { m_selectedCommand->Execute(); }
+
+void ConditionalCommand::End(bool interrupted) {
+  m_selectedCommand->End(interrupted);
+}
+
+bool ConditionalCommand::IsFinished() {
+  return m_selectedCommand->IsFinished();
+}
+
+bool ConditionalCommand::RunsWhenDisabled() const { return m_runsWhenDisabled; }