Update PR before trying to merge it

It probably makes sense to do things in this order rather than how we
were doing it before.

server/handler/pull_request.go

@@ -82,9 +82,6 @@ func (h *PullRequest) Handle(ctx context.Context, eventType, deliveryID string,
 	if err != nil {
 		return errors.Wrap(err, "failed to fetch configuration")
 	}
-	if err := h.ProcessPullRequest(ctx, pullCtx, client, config, pr); err != nil {
-		logger.Error().Err(errors.WithStack(err)).Msg("Error processing pull request")
-	}
 
 	if event.GetAction() == "labeled" || event.GetAction() == "opened" {
 		base, _ := pullCtx.Branches()
@@ -93,6 +90,10 @@ func (h *PullRequest) Handle(ctx context.Context, eventType, deliveryID string,
 		}
 	}
 
+	if err := h.ProcessPullRequest(ctx, pullCtx, client, config, pr); err != nil {
+		logger.Error().Err(errors.WithStack(err)).Msg("Error processing pull request")
+	}
+
 	return nil
 }