ObjectDirectory: extra logging on packfile exceptions

Display extra logging, including the exception with the associated
stacktrace, whenever a packFile can't be read and thus removed
from the packlist.

Change-Id: I97a4e31dc427bfcc0baae438dcbe2dcd4704b824
Signed-off-by: Luca Milanesio <luca.milanesio@gmail.com>
(cherry picked from commit 962babc4b2)

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

@@ -355,6 +355,7 @@ public class ObjectDirectory extends FileObjectDatabase {
 					// The hasObject call should have only touched the index,
 					// so any failure here indicates the index is unreadable
 					// by this process, and the pack is likewise not readable.
+					LOG.warn("Unable to read packfile " + p.getPackFile(), e);
 					removePack(p);
 				}
 			}
@@ -647,6 +648,7 @@ public class ObjectDirectory extends FileObjectDatabase {
 		if ((e instanceof CorruptObjectException)
 				|| (e instanceof PackInvalidException)) {
 			warnTmpl = JGitText.get().corruptPack;
+			LOG.warn("Packfile " + p.getPackFile() + " is corrupted", e);
 			// Assume the pack is corrupted, and remove it from the list.
 			removePack(p);
 		} else if (e instanceof FileNotFoundException) {