Add deploy directory detection (#1400)

Add Filesystem class for java and namespace methods for C++ for detecting deploy location.

wpilibj/src/main/java/edu/wpi/first/wpilibj/Filesystem.java

@@ -0,0 +1,58 @@
+/*----------------------------------------------------------------------------*/
+/* Copyright (c) 2008-2018 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.                                                               */
+/*----------------------------------------------------------------------------*/
+
+package edu.wpi.first.wpilibj;
+
+import java.io.File;
+
+/**
+ * Class for interacting with the Filesystem, particularly, interacting with
+ * FRC-related paths on the system, such as the launch and deploy directories.
+ *
+ * <p>This class is primarily used for obtaining resources in src/main/deploy, and
+ * the RoboRIO path /home/lvuser in a simulation-compatible way.</p>
+ */
+public final class Filesystem {
+  private Filesystem() { }
+
+  /**
+   * Obtains the current working path that the program was launched with.
+   * This is analogous to the `pwd` command on unix.
+   *
+   * @return The current working directory (launch directory)
+   */
+  public static File getLaunchDirectory() {
+    return new File(System.getProperty("user.dir")).getAbsoluteFile();
+  }
+
+  /**
+   * Obtains the operating directory of the program. On the roboRIO, this is
+   * /home/lvuser. In simulation, it is where the simulation was launched from
+   * (`pwd`).
+   *
+   * @return The operating directory
+   */
+  public static File getOperatingDirectory() {
+    if (RobotBase.isReal()) {
+      return new File("/home/lvuser");
+    } else {
+      return getLaunchDirectory();
+    }
+  }
+
+  /**
+   * Obtains the deploy directory of the program, which is the remote location
+   * src/main/deploy is deployed to by default. On the roboRIO, this is
+   * /home/lvuser/deploy. In simulation, it is where the simulation was launched
+   * from, in the subdirectory "deploy" (`pwd`/deploy).
+   *
+   * @return The deploy directory
+   */
+  public static File getDeployDirectory() {
+    return new File(getOperatingDirectory(), "deploy");
+  }
+}