Merge branch 'stable-4.5' into stable-4.6

* stable-4.5:
  Don't remove pack when FileNotFoundException is transient

Change-Id: Ic17c542d78a4cad48ff1ed77dcdc853a4ef2dc06
Signed-off-by: Matthias Sohn <matthias.sohn@sap.com>

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

 exceptionHookExecutionInterrupted=Execution of "{0}" hook interrupted.
 exceptionOccurredDuringAddingOfOptionToALogCommand=Exception occurred during adding of {0} as option to a Log command
 exceptionOccurredDuringReadingOfGIT_DIR=Exception occurred during reading of $GIT_DIR/{0}. {1}
-exceptionWhileReadingPack=ERROR: Exception caught while accessing pack file {0}, the pack file might be corrupt
+exceptionWhileReadingPack=ERROR: Exception caught while accessing pack file {0}, the pack file might be corrupt, {1}. Caught {2} consecutive errors while trying to read this pack.
 expectedACKNAKFoundEOF=Expected ACK/NAK, found EOF
 expectedACKNAKGot=Expected ACK/NAK, got: {0}
 expectedBooleanStringValue=Expected boolean string value
 packfileIsTruncatedNoParam=Packfile is truncated.
 packHandleIsStale=Pack file {0} handle is stale, removing it from pack list
 packHasUnresolvedDeltas=pack has unresolved deltas
-packInaccessible=Pack file {0} now inaccessible; removing it from pack list
+packInaccessible=Failed to access pack file {0},  caught {2} consecutive errors while trying to access this pack.
 packingCancelledDuringObjectsWriting=Packing cancelled during objects writing
 packObjectCountMismatch=Pack object count mismatch: pack {0} index {1}: {2}
 packRefs=Pack refs

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

 			for (PackFile p : pList.packs) {
 				try {
 					p.resolve(matches, id, RESOLVE_ABBREV_LIMIT);
+					p.resetTransientErrorCount();
 				} catch (IOException e) {
 					handlePackError(e, p);
 				}
 				for (PackFile p : pList.packs) {
 					try {
 						ObjectLoader ldr = p.get(curs, objectId);
+						p.resetTransientErrorCount();
 						if (ldr != null)
 							return ldr;
 					} catch (PackMismatchException e) {
 				for (PackFile p : pList.packs) {
 					try {
 						long len = p.getObjectSize(curs, id);
+						p.resetTransientErrorCount();
 						if (0 <= len)
 							return len;
 					} catch (PackMismatchException e) {
 			for (final PackFile p : pList.packs) {
 				try {
 					LocalObjectRepresentation rep = p.representation(curs, otp);
+					p.resetTransientErrorCount();
 					if (rep != null)
 						packer.select(otp, rep);
 				} catch (PackMismatchException e) {
 
 	private void handlePackError(IOException e, PackFile p) {
 		String warnTmpl = null;
+		int transientErrorCount = 0;
+		String errTmpl = JGitText.get().exceptionWhileReadingPack;
 		if ((e instanceof CorruptObjectException)
 				|| (e instanceof PackInvalidException)) {
 			warnTmpl = JGitText.get().corruptPack;
 			removePack(p);
 		} else if (e instanceof FileNotFoundException) {
 			if (p.getPackFile().exists()) {
-				warnTmpl = JGitText.get().packInaccessible;
+				errTmpl = JGitText.get().packInaccessible;
+				transientErrorCount = p.incrementTransientErrorCount();
 			} else {
 				warnTmpl = JGitText.get().packWasDeleted;
+				removePack(p);
 			}
-			removePack(p);
 		} else if (FileUtils.isStaleFileHandle(e)) {
 			warnTmpl = JGitText.get().packHandleIsStale;
 			removePack(p);
+		} else {
+			transientErrorCount = p.incrementTransientErrorCount();
 		}
 		if (warnTmpl != null) {
 			if (LOG.isDebugEnabled()) {
 						p.getPackFile().getAbsolutePath()));
 			}
 		} else {
-			// Don't remove the pack from the list, as the error may be
-			// transient.
-			LOG.error(MessageFormat.format(
-					JGitText.get().exceptionWhileReadingPack, p.getPackFile()
-							.getAbsolutePath()), e);
+			if (doLogExponentialBackoff(transientErrorCount)) {
+				// Don't remove the pack from the list, as the error may be
+				// transient.
+				LOG.error(MessageFormat.format(errTmpl,
+						p.getPackFile().getAbsolutePath()),
+						Integer.valueOf(transientErrorCount), e);
+			}
 		}
 	}
 
+	/**
+	 * @param n
+	 *            count of consecutive failures
+	 * @return @{code true} if i is a power of 2
+	 */
+	private boolean doLogExponentialBackoff(int n) {
+		return (n & (n - 1)) == 0;
+	}
+
 	@Override
 	InsertLooseObjectResult insertUnpackedObject(File tmp, ObjectId id,
 			boolean createDuplicate) throws IOException {

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

 import java.util.Comparator;
 import java.util.Iterator;
 import java.util.Set;
+import java.util.concurrent.atomic.AtomicInteger;
 import java.util.zip.CRC32;
 import java.util.zip.DataFormatException;
 import java.util.zip.Inflater;
 
 	private boolean invalidBitmap;
 
+	private AtomicInteger transientErrorCount = new AtomicInteger();
+
 	private byte[] packChecksum;
 
 	private PackIndex loadedIdx;
 		invalid = true;
 	}
 
+	int incrementTransientErrorCount() {
+		return transientErrorCount.incrementAndGet();
+	}
+
+	void resetTransientErrorCount() {
+		transientErrorCount.set(0);
+	}
+
 	private void readFully(final long position, final byte[] dstbuf,
 			int dstoff, final int cnt, final WindowCursor curs)
 			throws IOException {