Merge branch 'stable-2.15'

* stable-2.15:
  CommitValidators: Debug log when commit validation exception occurs

Change-Id: I66f1a697cdc4da7aad43ebf6ee201d31491c2410

java/com/google/gerrit/server/git/validators/CommitValidators.java

@@ -225,6 +225,7 @@ public class CommitValidators {
         messages.addAll(commitValidator.onCommitReceived(receiveEvent));
       }
     } catch (CommitValidationException e) {
+      log.debug("CommitValidationException occurred: {}", e.getFullMessage(), e);
       // Keep the old messages (and their order) in case of an exception
       messages.addAll(e.getMessages());
       throw new CommitValidationException(e.getMessage(), messages);