Merge branch 'stable-4.6'

* stable-4.6:
  GC: delete empty directories after purging loose objects
  GC.prune(Set<ObjectId>): return early if objects directory is empty

Change-Id: I3d6cacf80d3b4c69ba108e970855963bd9f6ee78
Signed-off-by: Matthias Sohn <matthias.sohn@sap.com>

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

@@ -455,7 +455,9 @@ public class GC {
 		Set<ObjectId> indexObjects = null;
 		File objects = repo.getObjectsDirectory();
 		String[] fanout = objects.list();
-		if (fanout != null && fanout.length > 0) {
+		if (fanout == null || fanout.length == 0) {
+			return;
+		}
 		pm.beginTask(JGitText.get().pruneLooseUnreferencedObjects,
 				fanout.length);
 		try {
@@ -493,9 +495,10 @@ public class GC {
 		} finally {
 			pm.endTask();
 		}
-		}
-		if (deletionCandidates.isEmpty())
+
+		if (deletionCandidates.isEmpty()) {
 			return;
+		}
 
 		checkCancelled();
 
@@ -576,12 +579,19 @@ public class GC {
 		// loose objects. Make a last check, though, to avoid deleting objects
 		// that could have been referenced while the candidates list was being
 		// built (by an incoming push, for example).
+		Set<File> touchedFanout = new HashSet<>();
 		for (File f : deletionCandidates.values()) {
 			if (f.lastModified() < expireDate) {
 				f.delete();
+				touchedFanout.add(f.getParentFile());
 			}
 		}
 
+		for (File f : touchedFanout) {
+			FileUtils.delete(f,
+					FileUtils.EMPTY_DIRECTORIES_ONLY | FileUtils.IGNORE_ERRORS);
+		}
+
 		repo.getObjectDatabase().close();
 	}