Unset userHome in FS.

This prevents arbitrary user settings state from leaking into our
tests.

Change-Id: If5f4230bfaede0bf9f688b2cf1a1a48de5740b55

gerrit-acceptance-framework/src/test/java/com/google/gerrit/acceptance/GitUtil.java

@@ -42,6 +42,7 @@ import org.eclipse.jgit.transport.RefSpec;
 import org.eclipse.jgit.transport.SshSessionFactory;
 import org.eclipse.jgit.util.FS;
 
+import java.io.File;
 import java.io.IOException;
 import java.util.List;
 import java.util.Properties;
@@ -103,12 +104,18 @@ public class GitUtil {
       Project.NameKey project, String uri) throws Exception {
     DfsRepositoryDescription desc =
         new DfsRepositoryDescription("clone of " + project.get());
+
+    FS fs = FS.detect();
+
+    // Avoid leaking user state into our tests.
+    fs.setUserHome(null);
+
     InMemoryRepository dest = new InMemoryRepository.Builder()
         .setRepositoryDescription(desc)
         // SshTransport depends on a real FS to read ~/.ssh/config, but
         // InMemoryRepository by default uses a null FS.
         // TODO(dborowitz): Remove when we no longer depend on SSH.
-        .setFS(FS.detect())
+        .setFS(fs)
         .build();
     Config cfg = dest.getConfig();
     cfg.setString("remote", "origin", "url", uri);