Merge branch 'stable-4.8' into stable-4.9

* stable-4.8:
  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: I6ab2b951dd94a9fc1c4f5283847a3e2ec37d0895
Signed-off-by: Matthias Sohn <matthias.sohn@sap.com>

4 files changed, 57 insertions, 2 deletions

diff --git a/org.eclipse.jgit/resources/org/eclipse/jgit/internal/JGitText.properties b/org.eclipse.jgit/resources/org/eclipse/jgit/internal/JGitText.properties
index 8bae60b0e3..81edcfb543 100644
--- a/org.eclipse.jgit/resources/org/eclipse/jgit/internal/JGitText.properties
+++ b/org.eclipse.jgit/resources/org/eclipse/jgit/internal/JGitText.properties
@@ -45,6 +45,7 @@ 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}.
diff --git a/org.eclipse.jgit/src/org/eclipse/jgit/internal/JGitText.java b/org.eclipse.jgit/src/org/eclipse/jgit/internal/JGitText.java
index 9d757a5226..ea99836953 100644
--- a/org.eclipse.jgit/src/org/eclipse/jgit/internal/JGitText.java
+++ b/org.eclipse.jgit/src/org/eclipse/jgit/internal/JGitText.java
@@ -104,6 +104,7 @@ 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;
diff --git a/org.eclipse.jgit/src/org/eclipse/jgit/internal/storage/file/GC.java b/org.eclipse.jgit/src/org/eclipse/jgit/internal/storage/file/GC.java
index 60d6652745..574f3b3367 100644
--- a/org.eclipse.jgit/src/org/eclipse/jgit/internal/storage/file/GC.java
+++ b/org.eclipse.jgit/src/org/eclipse/jgit/internal/storage/file/GC.java
@@ -904,6 +904,7 @@ public class GC {
 			throw new IOException(e);
 		}
 		prunePacked();
+		deleteEmptyRefsFolders();
 		deleteOrphans();
 		deleteTempPacksIdx();
 
@@ -920,6 +921,55 @@ 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>
diff --git a/org.eclipse.jgit/src/org/eclipse/jgit/internal/storage/file/RefDirectory.java b/org.eclipse.jgit/src/org/eclipse/jgit/internal/storage/file/RefDirectory.java
index bd39e65657..a3e9437d95 100644
--- a/org.eclipse.jgit/src/org/eclipse/jgit/internal/storage/file/RefDirectory.java
+++ b/org.eclipse.jgit/src/org/eclipse/jgit/internal/storage/file/RefDirectory.java
@@ -1273,8 +1273,11 @@ public class RefDirectory extends RefDatabase {
 		}
 		File dir = file.getParentFile();
 		for (int i = 0; i < depth; ++i) {
-			if (!dir.delete()) {
-				break; // ignore problem here
+			try {
+				Files.delete(dir.toPath());
+			} catch (IOException e) {
+				LOG.warn("Unable to remove path {}", dir, e);
+				break;
 			}
 			dir = dir.getParentFile();
 		}