Remove hardcoded target/trash from test cases

Buck does not create a target directory for the build output, this
is Maven specific and the project unit tests should not rely on it.

Instead follow the pattern used by org.eclipse.jgit.test which is to
create a temporary directory in the system temporary folder, and
configure the Maven surefire plugin to use the target directory.

Change-Id: Iebe5093332343a90f51080614e083aac0d29c26d

org.eclipse.jgit.java7.test/pom.xml

@@ -118,7 +118,7 @@
       <plugin>
         <artifactId>maven-surefire-plugin</artifactId>
         <configuration>
-          <argLine>-Xmx256m -Dfile.encoding=UTF-8</argLine>
+          <argLine>-Xmx256m -Dfile.encoding=UTF-8 -Djava.io.tmpdir=${project.build.directory}</argLine>
         </configuration>
       </plugin>
     </plugins>

org.eclipse.jgit.java7.test/src/org/eclipse/jgit/util/FSJava7Test.java

@@ -58,13 +58,13 @@ import org.junit.Before;
 import org.junit.Test;
 
 public class FSJava7Test {
-
-	private final File trash = new File(new File("target"), "trash");
+	private File trash;
 
 	@Before
 	public void setUp() throws Exception {
-		FileUtils.delete(trash, FileUtils.RECURSIVE | FileUtils.RETRY | FileUtils.SKIP_MISSING);
-		assertTrue(trash.mkdirs());
+		trash = File.createTempFile("tmp_", "");
+		trash.delete();
+		assertTrue("mkdir " + trash, trash.mkdir());
 	}
 
 	@After

org.eclipse.jgit.test/tst/org/eclipse/jgit/internal/storage/file/FileSnapshotTest.java

@@ -61,7 +61,14 @@ public class FileSnapshotTest {
 
 	private List<File> files = new ArrayList<File>();
 
-	private final File trash = new File(new File("target"), "trash");
+	private File trash;
+
+	@Before
+	public void setUp() throws Exception {
+		trash = File.createTempFile("tmp_", "");
+		trash.delete();
+		assertTrue("mkdir " + trash, trash.mkdir());
+	}
 
 	@Before
 	@After

org.eclipse.jgit.test/tst/org/eclipse/jgit/storage/file/FileBasedConfigTest.java

@@ -44,6 +44,7 @@ package org.eclipse.jgit.storage.file;
 
 import static org.junit.Assert.assertArrayEquals;
 import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertTrue;
 
 import java.io.ByteArrayOutputStream;
 import java.io.File;
@@ -55,6 +56,7 @@ import org.eclipse.jgit.util.FS;
 import org.eclipse.jgit.util.FileUtils;
 import org.eclipse.jgit.util.IO;
 import org.junit.After;
+import org.junit.Before;
 import org.junit.Test;
 
 public class FileBasedConfigTest {
@@ -73,7 +75,14 @@ public class FileBasedConfigTest {
 	private static final String CONTENT2 = "[" + USER + "]\n\t" + NAME + " = "
 			+ BOB + "\n";
 
-	private final File trash = new File(new File("target"), "trash");
+	private File trash;
+
+	@Before
+	public void setUp() throws Exception {
+		trash = File.createTempFile("tmp_", "");
+		trash.delete();
+		assertTrue("mkdir " + trash, trash.mkdir());
+	}
 
 	@After
 	public void tearDown() throws Exception {

org.eclipse.jgit.test/tst/org/eclipse/jgit/util/FileUtilTest.java

@@ -57,12 +57,13 @@ import org.junit.Before;
 import org.junit.Test;
 
 public class FileUtilTest {
-
-	private final File trash = new File(new File("target"), "trash");
+	private File trash;
 
 	@Before
 	public void setUp() throws Exception {
-		assertTrue(trash.mkdirs());
+		trash = File.createTempFile("tmp_", "");
+		trash.delete();
+		assertTrue("mkdir " + trash, trash.mkdir());
 	}
 
 	@After