Add CommandLinePathFactory to CommandEnvironment

Progress on bazelbuild#15856

Author: Yannic

src/main/java/com/google/devtools/build/lib/runtime/CommandEnvironment.java

@@ -107,6 +107,7 @@ public class CommandEnvironment {
   private final ImmutableList.Builder<Any> responseExtensions = ImmutableList.builder();
   private final Consumer<String> shutdownReasonConsumer;
   private final BuildResultListener buildResultListener;
+  private final CommandLinePathFactory commandLinePathFactory;
 
   private OutputService outputService;
   private String workspaceName;
@@ -273,6 +274,23 @@ public void exit(AbruptExitException exception) {
     }
     this.buildResultListener = new BuildResultListener();
     this.eventBus.register(this.buildResultListener);
+
+    ImmutableMap.Builder<String, Path> wellKnownRoots = ImmutableMap.builder();
+    // This is necessary because some tests don't have a workspace set.
+    putIfValueNotNull(wellKnownRoots, "workspace", directories.getWorkspace());
+
+    this.commandLinePathFactory =
+        new CommandLinePathFactory(runtime.getFileSystem(), wellKnownRoots.build());
+  }
+
+  private static <K, V> void putIfValueNotNull(
+      ImmutableMap.Builder<K, V> map, K key, @Nullable V value) {
+    Preconditions.checkNotNull(map);
+    Preconditions.checkNotNull(key);
+
+    if (value != null) {
+      map.put(key, value);
+    }
   }
 
   private Path computeWorkingDirectory(CommonCommandOptions commandOptions)
@@ -840,4 +858,8 @@ public void addResponseExtensions(Iterable<Any> extensions) {
   public BuildResultListener getBuildResultListener() {
     return buildResultListener;
   }
+
+  public CommandLinePathFactory getCommandLinePathFactory() {
+    return commandLinePathFactory;
+  }
 }