Extend FileUtils.delete with option to delete empty directories only

The new option EMPTY_DIRECTORIES_ONLY will make delete() only delete
empty directories. Any attempt to delete files will fail. Can be
combined with RECURSIVE to wipe out entire tree structures and
IGNORE_ERRORS to silently ignore any files or non-empty directories.

Change-Id: Icaa9a30e5302ee5c0ba23daad11c7b93e26b7445
Signed-off-by: Robin Stocker <robin@nibor.org>

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

@@ -43,6 +43,8 @@
 
 package org.eclipse.jgit.util;
 
+import static org.hamcrest.MatcherAssert.assertThat;
+import static org.hamcrest.Matchers.endsWith;
 import static org.junit.Assert.assertFalse;
 import static org.junit.Assert.assertTrue;
 import static org.junit.Assert.fail;
@@ -175,6 +177,7 @@ public class FileUtilTest {
 		assertTrue(f.delete());
 	}
 
+	@Test
 	public void testCreateNewFile() throws IOException {
 		File f = new File(trash, "x");
 		FileUtils.createNewFile(f);
@@ -190,4 +193,47 @@ public class FileUtilTest {
 		FileUtils.delete(f);
 	}
 
+	@Test
+	public void testDeleteEmptyTreeOk() throws IOException {
+		File t = new File(trash, "t");
+		FileUtils.mkdir(t);
+		FileUtils.mkdir(new File(t, "d"));
+		FileUtils.mkdir(new File(new File(t, "d"), "e"));
+		FileUtils.delete(t, FileUtils.EMPTY_DIRECTORIES_ONLY | FileUtils.RECURSIVE);
+		assertFalse(t.exists());
+	}
+
+	@Test
+	public void testDeleteNotEmptyTreeNotOk() throws IOException {
+		File t = new File(trash, "t");
+		FileUtils.mkdir(t);
+		FileUtils.mkdir(new File(t, "d"));
+		File f = new File(new File(t, "d"), "f");
+		FileUtils.createNewFile(f);
+		FileUtils.mkdir(new File(new File(t, "d"), "e"));
+		try {
+			FileUtils.delete(t, FileUtils.EMPTY_DIRECTORIES_ONLY | FileUtils.RECURSIVE);
+			fail("expected failure to delete f");
+		} catch (IOException e) {
+			assertThat(e.getMessage(), endsWith(f.getAbsolutePath()));
+		}
+		assertTrue(t.exists());
+	}
+
+	@Test
+	public void testDeleteNotEmptyTreeNotOkButIgnoreFail() throws IOException {
+		File t = new File(trash, "t");
+		FileUtils.mkdir(t);
+		FileUtils.mkdir(new File(t, "d"));
+		File f = new File(new File(t, "d"), "f");
+		FileUtils.createNewFile(f);
+		File e = new File(new File(t, "d"), "e");
+		FileUtils.mkdir(e);
+		FileUtils.delete(t, FileUtils.EMPTY_DIRECTORIES_ONLY | FileUtils.RECURSIVE
+				| FileUtils.IGNORE_ERRORS);
+		// Should have deleted as much as possible, but not all
+		assertTrue(t.exists());
+		assertTrue(f.exists());
+		assertFalse(e.exists());
+	}
 }

org.eclipse.jgit/src/org/eclipse/jgit/util/FileUtils.java

@@ -83,6 +83,14 @@ public class FileUtils {
 	 */
 	public static final int IGNORE_ERRORS = 8;
 
+	/**
+	 * Option to only delete empty directories. This option can be combined with
+	 * {@link #RECURSIVE}
+	 *
+	 * @since 2.4
+	 */
+	public static final int EMPTY_DIRECTORIES_ONLY = 16;
+
 	/**
 	 * Delete file or empty folder
 	 *
@@ -126,7 +134,22 @@ public class FileUtils {
 					delete(c, options);
 			}
 		}
-		if (!f.delete()) {
+
+		boolean delete = false;
+		if ((options & EMPTY_DIRECTORIES_ONLY) != 0) {
+			if (f.isDirectory()) {
+				delete = true;
+			} else {
+				if ((options & IGNORE_ERRORS) == 0)
+					throw new IOException(MessageFormat.format(
+							JGitText.get().deleteFileFailed,
+							f.getAbsolutePath()));
+			}
+		} else {
+			delete = true;
+		}
+
+		if (delete && !f.delete()) {
 			if ((options & RETRY) != 0 && f.exists()) {
 				for (int i = 1; i < 10; i++) {
 					try {