Merge branch 'stable-4.9' into stable-4.10

* stable-4.9:
  Prepare 4.7.3-SNAPSHOT builds
  JGit v4.7.2.201807261330-r
  Delete all loose refs empty directories
  Use java.nio to delete path to get detailed errors
  GC: Remove empty references folders
  Do not ignore path deletion errors

Change-Id: Ie7029bc91621af32e7bfd2e0d76a424b991b1995
Signed-off-by: Matthias Sohn <matthias.sohn@sap.com>

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

@@ -0,0 +1,132 @@
+/*
+ * Copyright (C) 2018 Ericsson
+ * and other copyright owners as documented in the project's IP log.
+ *
+ * This program and the accompanying materials are made available
+ * under the terms of the Eclipse Distribution License v1.0 which
+ * accompanies this distribution, is reproduced below, and is
+ * available at http://www.eclipse.org/org/documents/edl-v10.php
+ *
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or
+ * without modification, are permitted provided that the following
+ * conditions are met:
+ *
+ * - Redistributions of source code must retain the above copyright
+ *   notice, this list of conditions and the following disclaimer.
+ *
+ * - Redistributions in binary form must reproduce the above
+ *   copyright notice, this list of conditions and the following
+ *   disclaimer in the documentation and/or other materials provided
+ *   with the distribution.
+ *
+ * - Neither the name of the Eclipse Foundation, Inc. nor the
+ *   names of its contributors may be used to endorse or promote
+ *   products derived from this software without specific prior
+ *   written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND
+ * CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES,
+ * INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
+ * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
+ * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
+ * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
+ * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+ * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
+ * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
+ * ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+package org.eclipse.jgit.internal.storage.file;
+
+import static org.junit.Assert.assertFalse;
+import static org.junit.Assert.assertTrue;
+
+import java.io.IOException;
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.nio.file.Paths;
+import java.nio.file.attribute.FileTime;
+import java.time.Instant;
+
+import org.junit.Before;
+import org.junit.Test;
+
+public class GcDeleteEmptyRefsFoldersTest extends GcTestCase {
+	private static final String REF_FOLDER_01 = "A/B/01";
+	private static final String REF_FOLDER_02 = "C/D/02";
+
+	private Path refsDir;
+	private Path heads;
+
+	@Override
+	@Before
+	public void setUp() throws Exception {
+		super.setUp();
+		refsDir = Paths.get(repo.getDirectory().getAbsolutePath())
+				.resolve("refs");
+		heads = refsDir.resolve("heads");
+	}
+
+	@Test
+	public void emptyRefFoldersAreDeleted() throws Exception {
+		FileTime fileTime = FileTime.from(Instant.now().minusSeconds(31));
+		Path refDir01 = Files.createDirectories(heads.resolve(REF_FOLDER_01));
+		Path refDir02 = Files.createDirectories(heads.resolve(REF_FOLDER_02));
+		setLastModifiedTime(fileTime, heads, REF_FOLDER_01);
+		setLastModifiedTime(fileTime, heads, REF_FOLDER_02);
+		assertTrue(refDir01.toFile().exists());
+		assertTrue(refDir02.toFile().exists());
+		gc.gc();
+
+		assertFalse(refDir01.toFile().exists());
+		assertFalse(refDir01.getParent().toFile().exists());
+		assertFalse(refDir01.getParent().getParent().toFile().exists());
+		assertFalse(refDir02.toFile().exists());
+		assertFalse(refDir02.getParent().toFile().exists());
+		assertFalse(refDir02.getParent().getParent().toFile().exists());
+	}
+
+	private void setLastModifiedTime(FileTime fileTime, Path path, String folder) throws IOException {
+		long numParents = folder.chars().filter(c -> c == '/').count();
+		Path folderPath = path.resolve(folder);
+		for(int folderLevel = 0; folderLevel <= numParents; folderLevel ++ ) {
+			Files.setLastModifiedTime(folderPath, fileTime);
+			folderPath = folderPath.getParent();
+		}
+	}
+
+	@Test
+	public void emptyRefFoldersAreKeptIfTheyAreTooRecent()
+			throws Exception {
+		Path refDir01 = Files.createDirectories(heads.resolve(REF_FOLDER_01));
+		Path refDir02 = Files.createDirectories(heads.resolve(REF_FOLDER_02));
+		assertTrue(refDir01.toFile().exists());
+		assertTrue(refDir02.toFile().exists());
+		gc.gc();
+
+		assertTrue(refDir01.toFile().exists());
+		assertTrue(refDir02.toFile().exists());
+	}
+
+	@Test
+	public void nonEmptyRefsFoldersAreKept() throws Exception {
+		Path refDir01 = Files.createDirectories(heads.resolve(REF_FOLDER_01));
+		Path refDir02 = Files.createDirectories(heads.resolve(REF_FOLDER_02));
+		Path ref01 = Files.createFile(refDir01.resolve("ref01"));
+		Path ref02 = Files.createFile(refDir01.resolve("ref02"));
+		assertTrue(refDir01.toFile().exists());
+		assertTrue(refDir02.toFile().exists());
+		assertTrue(ref01.toFile().exists());
+		assertTrue(ref02.toFile().exists());
+		gc.gc();
+		assertTrue(refDir01.toFile().exists());
+		assertTrue(refDir02.toFile().exists());
+		assertTrue(ref01.toFile().exists());
+		assertTrue(ref02.toFile().exists());
+	}
+}

org.eclipse.jgit/resources/org/eclipse/jgit/internal/JGitText.properties

@@ -47,6 +47,7 @@ branchNameInvalid=Branch name {0} is not allowed
 buildingBitmaps=Building bitmaps
 cachedPacksPreventsIndexCreation=Using cached packs prevents index creation
 cachedPacksPreventsListingObjects=Using cached packs prevents listing objects
+cannotAccessLastModifiedForSafeDeletion=Unable to access lastModifiedTime of file {0}, skip deletion since we cannot safely avoid race condition
 cannotBeCombined=Cannot be combined.
 cannotBeRecursiveWhenTreesAreIncluded=TreeWalk shouldn't be recursive when tree objects are included.
 cannotChangeActionOnComment=Cannot change action on comment line in git-rebase-todo file, old action: {0}, new action: {1}.

org.eclipse.jgit/src/org/eclipse/jgit/internal/JGitText.java

@@ -108,6 +108,7 @@ public class JGitText extends TranslationBundle {
 	/***/ public String buildingBitmaps;
 	/***/ public String cachedPacksPreventsIndexCreation;
 	/***/ public String cachedPacksPreventsListingObjects;
+	/***/ public String cannotAccessLastModifiedForSafeDeletion;
 	/***/ public String cannotBeCombined;
 	/***/ public String cannotBeRecursiveWhenTreesAreIncluded;
 	/***/ public String cannotChangeActionOnComment;

org.eclipse.jgit/src/org/eclipse/jgit/internal/storage/file/GC.java

@@ -907,6 +907,7 @@ public class GC {
 			throw new IOException(e);
 		}
 		prunePacked();
+		deleteEmptyRefsFolders();
 		deleteOrphans();
 		deleteTempPacksIdx();
 
@@ -923,6 +924,55 @@ public class GC {
 		return ref.getName().startsWith(Constants.R_TAGS);
 	}
 
+	private void deleteEmptyRefsFolders() throws IOException {
+		Path refs = repo.getDirectory().toPath().resolve(Constants.R_REFS);
+		// Avoid deleting a folder that was created after the threshold so that concurrent
+		// operations trying to create a reference are not impacted
+		Instant threshold = Instant.now().minus(30, ChronoUnit.SECONDS);
+		try (Stream<Path> entries = Files.list(refs)) {
+			Iterator<Path> iterator = entries.iterator();
+			while (iterator.hasNext()) {
+				try (Stream<Path> s = Files.list(iterator.next())) {
+					s.filter(path -> canBeSafelyDeleted(path, threshold)).forEach(this::deleteDir);
+				}
+			}
+		}
+	}
+
+	private boolean canBeSafelyDeleted(Path path, Instant threshold) {
+		try {
+			return Files.getLastModifiedTime(path).toInstant().isBefore(threshold);
+		}
+		catch (IOException e) {
+			LOG.warn(MessageFormat.format(
+					JGitText.get().cannotAccessLastModifiedForSafeDeletion,
+					path), e);
+			return false;
+		}
+	}
+
+	private void deleteDir(Path dir) {
+		try (Stream<Path> dirs = Files.walk(dir)) {
+			dirs.filter(this::isDirectory).sorted(Comparator.reverseOrder())
+					.forEach(this::delete);
+		} catch (IOException e) {
+			LOG.error(e.getMessage(), e);
+		}
+	}
+
+	private boolean isDirectory(Path p) {
+		return p.toFile().isDirectory();
+	}
+
+	private void delete(Path d) {
+		try {
+			Files.delete(d);
+		} catch (IOException e) {
+			LOG.error(MessageFormat.format(JGitText.get().cannotDeleteFile, d),
+					e);
+		}
+	}
+
 	/**
 	 * Deletes orphans
 	 * <p>

org.eclipse.jgit/src/org/eclipse/jgit/internal/storage/file/RefDirectory.java

@@ -1284,8 +1284,11 @@ public class RefDirectory extends RefDatabase {
 		}
 		File dir = file.getParentFile();
 		for (int i = 0; i < depth; ++i) {
-			if (!dir.delete()) {
+			try {
-				break; // ignore problem here
+				Files.delete(dir.toPath());
+			} catch (IOException e) {
+				LOG.warn("Unable to remove path {}", dir, e);
+				break;
 			}
 			dir = dir.getParentFile();
 		}