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.

wpilibOldCommands/src/main/native/cpp/commands/ConditionalCommand.cpp

@@ -0,0 +1,80 @@
+/*----------------------------------------------------------------------------*/
+/* Copyright (c) 2017-2019 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 "frc/commands/ConditionalCommand.h"
+
+#include "frc/commands/Scheduler.h"
+
+using namespace frc;
+
+static void RequireAll(Command& command, Command* onTrue, Command* onFalse) {
+  if (onTrue != nullptr) {
+    for (auto requirement : onTrue->GetRequirements())
+      command.Requires(requirement);
+  }
+  if (onFalse != nullptr) {
+    for (auto requirement : onFalse->GetRequirements())
+      command.Requires(requirement);
+  }
+}
+
+ConditionalCommand::ConditionalCommand(Command* onTrue, Command* onFalse) {
+  m_onTrue = onTrue;
+  m_onFalse = onFalse;
+
+  RequireAll(*this, onTrue, onFalse);
+}
+
+ConditionalCommand::ConditionalCommand(const wpi::Twine& name, Command* onTrue,
+                                       Command* onFalse)
+    : Command(name) {
+  m_onTrue = onTrue;
+  m_onFalse = onFalse;
+
+  RequireAll(*this, onTrue, onFalse);
+}
+
+void ConditionalCommand::_Initialize() {
+  if (Condition()) {
+    m_chosenCommand = m_onTrue;
+  } else {
+    m_chosenCommand = m_onFalse;
+  }
+
+  if (m_chosenCommand != nullptr) {
+    // This is a hack to make cancelling the chosen command inside a
+    // CommandGroup work properly
+    m_chosenCommand->ClearRequirements();
+
+    m_chosenCommand->Start();
+  }
+  Command::_Initialize();
+}
+
+void ConditionalCommand::_Cancel() {
+  if (m_chosenCommand != nullptr && m_chosenCommand->IsRunning()) {
+    m_chosenCommand->Cancel();
+  }
+
+  Command::_Cancel();
+}
+
+bool ConditionalCommand::IsFinished() {
+  if (m_chosenCommand != nullptr) {
+    return m_chosenCommand->IsCompleted();
+  } else {
+    return true;
+  }
+}
+
+void ConditionalCommand::_Interrupted() {
+  if (m_chosenCommand != nullptr && m_chosenCommand->IsRunning()) {
+    m_chosenCommand->Cancel();
+  }
+
+  Command::_Interrupted();
+}